How to use the ufo2ft.fontInfoData.getAttrWithFallback function in ufo2ft

# panose
        data = getAttrWithFallback(font.info, "openTypeOS2Panose")
        panose = Panose()
        panose.bFamilyType = data[0]
        panose.bSerifStyle = data[1]
        panose.bWeight = data[2]
        panose.bProportion = data[3]
        panose.bContrast = data[4]
        panose.bStrokeVariation = data[5]
        panose.bArmStyle = data[6]
        panose.bLetterForm = data[7]
        panose.bMidline = data[8]
        panose.bXHeight = data[9]
        os2.panose = panose
        # Unicode ranges
        uniRanges = getAttrWithFallback(font.info, "openTypeOS2UnicodeRanges")
        os2.ulUnicodeRange1 = intListToNum(uniRanges, 0, 32)
        os2.ulUnicodeRange2 = intListToNum(uniRanges, 32, 32)
        os2.ulUnicodeRange3 = intListToNum(uniRanges, 64, 32)
        os2.ulUnicodeRange4 = intListToNum(uniRanges, 96, 32)
        # codepage ranges
        codepageRanges = getAttrWithFallback(font.info, "openTypeOS2CodePageRanges")
        os2.ulCodePageRange1 = intListToNum(codepageRanges, 0, 32)
        os2.ulCodePageRange2 = intListToNum(codepageRanges, 32, 32)
        # vendor id
        os2.achVendID = tounicode(
            getAttrWithFallback(font.info, "openTypeOS2VendorID"),
            encoding="ascii", errors="ignore")
        # vertical metrics
        os2.sxHeight = round(getAttrWithFallback(font.info, "xHeight"))
        os2.sCapHeight = round(getAttrWithFallback(font.info, "capHeight"))
        os2.sTypoAscender = round(getAttrWithFallback(font.info, "openTypeOS2TypoAscender"))

height, top = vmtx[glyphName]
            heights.append(height)
            bounds = self.glyphBoundingBoxes[glyphName]
            if bounds is None:
                continue
            bottom = height - top - (bounds.yMax - bounds.yMin)
            tops.append(top)
            bottoms.append(bottom)
        vhea.advanceHeightMax = max(heights)
        vhea.minTopSideBearing = max(tops)
        vhea.minBottomSideBearing = max(bottoms)
        vhea.yMaxExtent = vhea.minTopSideBearing - (head.yMax - head.yMin)
        # misc
        vhea.caretSlopeRise = getAttrWithFallback(font.info, "openTypeVheaCaretSlopeRise")
        vhea.caretSlopeRun = getAttrWithFallback(font.info, "openTypeVheaCaretSlopeRun")
        vhea.caretOffset = getAttrWithFallback(font.info, "openTypeVheaCaretOffset")
        vhea.reserved0 = 0
        vhea.reserved1 = 0
        vhea.reserved2 = 0
        vhea.reserved3 = 0
        vhea.reserved4 = 0
        vhea.metricDataFormat = 0
        # glyph count
        vhea.numberOfVMetrics = len(self.allGlyphs)

font = self.ufo
        os2.version = 0x0004
        # average glyph width
        widths = [glyph.width for glyph in self.allGlyphs.values() if glyph.width > 0]
        os2.xAvgCharWidth = round(sum(widths) / len(widths))
        # weight and width classes
        os2.usWeightClass = getAttrWithFallback(font.info, "openTypeOS2WeightClass")
        os2.usWidthClass = getAttrWithFallback(font.info, "openTypeOS2WidthClass")
        # embedding
        os2.fsType = intListToNum(getAttrWithFallback(font.info, "openTypeOS2Type"), 0, 16)

        # subscript, superscript, strikeout values, taken from AFDKO:
        # FDK/Tools/Programs/makeotf/makeotf_lib/source/hotconv/hot.c
        unitsPerEm = getAttrWithFallback(font.info, "unitsPerEm")
        italicAngle = getAttrWithFallback(font.info, "italicAngle")
        xHeight = getAttrWithFallback(font.info, "xHeight")
        def adjustOffset(offset, angle):
            """Adjust Y offset based on italic angle, to get X offset."""
            return offset * math.tan(math.radians(-angle)) if angle else 0

        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptXSize")
        if v is None:
            v = unitsPerEm * 0.65
        os2.ySubscriptXSize = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptYSize")
        if v is None:
            v = unitsPerEm * 0.6
        os2.ySubscriptYSize = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptYOffset")
        if v is None:
            v = unitsPerEm * 0.075
        os2.ySubscriptYOffset = round(v)

os2.fsType = intListToNum(getAttrWithFallback(font.info, "openTypeOS2Type"), 0, 16)

        # subscript, superscript, strikeout values, taken from AFDKO:
        # FDK/Tools/Programs/makeotf/makeotf_lib/source/hotconv/hot.c
        unitsPerEm = getAttrWithFallback(font.info, "unitsPerEm")
        italicAngle = getAttrWithFallback(font.info, "italicAngle")
        xHeight = getAttrWithFallback(font.info, "xHeight")
        def adjustOffset(offset, angle):
            """Adjust Y offset based on italic angle, to get X offset."""
            return offset * math.tan(math.radians(-angle)) if angle else 0

        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptXSize")
        if v is None:
            v = unitsPerEm * 0.65
        os2.ySubscriptXSize = _roundInt(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptYSize")
        if v is None:
            v = unitsPerEm * 0.6
        os2.ySubscriptYSize = _roundInt(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptYOffset")
        if v is None:
            v = unitsPerEm * 0.075
        os2.ySubscriptYOffset = _roundInt(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptXOffset")
        if v is None:
            v = adjustOffset(-os2.ySubscriptYOffset, italicAngle)
        os2.ySubscriptXOffset = _roundInt(v)

        v = getAttrWithFallback(font.info, "openTypeOS2SuperscriptXSize")
        if v is None:
            v = os2.ySubscriptXSize
        os2.ySuperscriptXSize = _roundInt(v)

**This should not be called externally.** Subclasses
        may override or supplement this method to handle the
        table creation in a different way if desired.
        """

        self.otf["head"] = head = newTable("head")
        font = self.ufo
        head.checkSumAdjustment = 0
        head.tableVersion = 1.0
        head.magicNumber = 0x5F0F3CF5

        # version numbers
        # limit minor version to 3 digits as recommended in OpenType spec:
        # https://www.microsoft.com/typography/otspec/recom.htm
        versionMajor = getAttrWithFallback(font.info, "versionMajor")
        versionMinor = getAttrWithFallback(font.info, "versionMinor")
        fullFontRevision = float("%d.%03d" % (versionMajor, versionMinor))
        head.fontRevision = round(fullFontRevision, 3)
        if head.fontRevision != fullFontRevision:
            logger.warning(
                "Minor version in %s has too many digits and won't fit into "
                "the head table's fontRevision field; rounded to %s.",
                fullFontRevision, head.fontRevision)

        # upm
        head.unitsPerEm = getAttrWithFallback(font.info, "unitsPerEm")

        # times
        head.created = dateStringToTimeValue(getAttrWithFallback(font.info, "openTypeHeadCreated")) - mac_epoch_diff
        head.modified = dateStringToTimeValue(dateStringForNow()) - mac_epoch_diff

        # bounding box

v = unitsPerEm * 0.6
        os2.ySubscriptYSize = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptYOffset")
        if v is None:
            v = unitsPerEm * 0.075
        os2.ySubscriptYOffset = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SubscriptXOffset")
        if v is None:
            v = adjustOffset(-os2.ySubscriptYOffset, italicAngle)
        os2.ySubscriptXOffset = round(v)

        v = getAttrWithFallback(font.info, "openTypeOS2SuperscriptXSize")
        if v is None:
            v = os2.ySubscriptXSize
        os2.ySuperscriptXSize = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SuperscriptYSize")
        if v is None:
            v = os2.ySubscriptYSize
        os2.ySuperscriptYSize = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SuperscriptYOffset")
        if v is None:
            v = unitsPerEm * 0.35
        os2.ySuperscriptYOffset = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SuperscriptXOffset")
        if v is None:
            v = adjustOffset(os2.ySuperscriptYOffset, italicAngle)
        os2.ySuperscriptXOffset = round(v)

        v = getAttrWithFallback(font.info, "openTypeOS2StrikeoutSize")
        if v is None:
            v = getAttrWithFallback(font.info, "postscriptUnderlineThickness")
        os2.yStrikeoutSize = round(v)

2: styleName,
            3: getAttrWithFallback(font.info, "openTypeNameUniqueID"),
            4: fullName,
            5: getAttrWithFallback(font.info, "openTypeNameVersion"),
            6: getAttrWithFallback(font.info, "postscriptFontName"),
            7: getAttrWithFallback(font.info, "trademark"),
            8: getAttrWithFallback(font.info, "openTypeNameManufacturer"),
            9: getAttrWithFallback(font.info, "openTypeNameDesigner"),
            10: getAttrWithFallback(font.info, "openTypeNameDescription"),
            11: getAttrWithFallback(font.info, "openTypeNameManufacturerURL"),
            12: getAttrWithFallback(font.info, "openTypeNameDesignerURL"),
            13: getAttrWithFallback(font.info, "openTypeNameLicense"),
            14: getAttrWithFallback(font.info, "openTypeNameLicenseURL"),
            16: getAttrWithFallback(
                font.info, "openTypeNamePreferredFamilyName"),
            17: getAttrWithFallback(
                font.info, "openTypeNamePreferredSubfamilyName"),
        }

        # don't add typographic names if they are the same as the legacy ones
        if nameVals[1] == nameVals[16]:
            del nameVals[16]
        if nameVals[2] == nameVals[17]:
            del nameVals[17]
        # postscript font name
        if nameVals[6]:
            nameVals[6] = normalizeStringForPostscript(nameVals[6])

        for nameId in sorted(nameVals.keys()):
            nameVal = nameVals[nameId]
            if not nameVal:
                continue

panose.bProportion = data[3]
        panose.bContrast = data[4]
        panose.bStrokeVariation = data[5]
        panose.bArmStyle = data[6]
        panose.bLetterForm = data[7]
        panose.bMidline = data[8]
        panose.bXHeight = data[9]
        os2.panose = panose
        # Unicode ranges
        uniRanges = getAttrWithFallback(font.info, "openTypeOS2UnicodeRanges")
        os2.ulUnicodeRange1 = intListToNum(uniRanges, 0, 32)
        os2.ulUnicodeRange2 = intListToNum(uniRanges, 32, 32)
        os2.ulUnicodeRange3 = intListToNum(uniRanges, 64, 32)
        os2.ulUnicodeRange4 = intListToNum(uniRanges, 96, 32)
        # codepage ranges
        codepageRanges = getAttrWithFallback(font.info, "openTypeOS2CodePageRanges")
        os2.ulCodePageRange1 = intListToNum(codepageRanges, 0, 32)
        os2.ulCodePageRange2 = intListToNum(codepageRanges, 32, 32)
        # vendor id
        os2.achVendID = tounicode(
            getAttrWithFallback(font.info, "openTypeOS2VendorID"),
            encoding="ascii", errors="ignore")
        # vertical metrics
        os2.sxHeight = _roundInt(getAttrWithFallback(font.info, "xHeight"))
        os2.sCapHeight = _roundInt(getAttrWithFallback(font.info, "capHeight"))
        os2.sTypoAscender = _roundInt(getAttrWithFallback(font.info, "openTypeOS2TypoAscender"))
        os2.sTypoDescender = _roundInt(getAttrWithFallback(font.info, "openTypeOS2TypoDescender"))
        os2.sTypoLineGap = _roundInt(getAttrWithFallback(font.info, "openTypeOS2TypoLineGap"))
        os2.usWinAscent = _roundInt(getAttrWithFallback(font.info, "openTypeOS2WinAscent"))
        os2.usWinDescent = _roundInt(getAttrWithFallback(font.info, "openTypeOS2WinDescent"))
        # style mapping
        selection = list(getAttrWithFallback(font.info, "openTypeOS2Selection"))

fullName = familyName
        if styleName != "Regular":
            fullName += " %s" % styleName

        nameVals = {
            0: getAttrWithFallback(font.info, "copyright"),
            1: familyName,
            2: styleName,
            3: getAttrWithFallback(font.info, "openTypeNameUniqueID"),
            4: fullName,
            5: getAttrWithFallback(font.info, "openTypeNameVersion"),
            6: getAttrWithFallback(font.info, "postscriptFontName"),
            7: getAttrWithFallback(font.info, "trademark"),
            8: getAttrWithFallback(font.info, "openTypeNameManufacturer"),
            9: getAttrWithFallback(font.info, "openTypeNameDesigner"),
            10: getAttrWithFallback(font.info, "openTypeNameDescription"),
            11: getAttrWithFallback(font.info, "openTypeNameManufacturerURL"),
            12: getAttrWithFallback(font.info, "openTypeNameDesignerURL"),
            13: getAttrWithFallback(font.info, "openTypeNameLicense"),
            14: getAttrWithFallback(font.info, "openTypeNameLicenseURL"),
            16: getAttrWithFallback(
                font.info, "openTypeNamePreferredFamilyName"),
            17: getAttrWithFallback(
                font.info, "openTypeNamePreferredSubfamilyName"),
        }

        # don't add typographic names if they are the same as the legacy ones
        if nameVals[1] == nameVals[16]:
            del nameVals[16]
        if nameVals[2] == nameVals[17]:
            del nameVals[17]
        # postscript font name

v = os2.ySubscriptYSize
        os2.ySuperscriptYSize = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SuperscriptYOffset")
        if v is None:
            v = unitsPerEm * 0.35
        os2.ySuperscriptYOffset = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2SuperscriptXOffset")
        if v is None:
            v = adjustOffset(os2.ySuperscriptYOffset, italicAngle)
        os2.ySuperscriptXOffset = round(v)

        v = getAttrWithFallback(font.info, "openTypeOS2StrikeoutSize")
        if v is None:
            v = getAttrWithFallback(font.info, "postscriptUnderlineThickness")
        os2.yStrikeoutSize = round(v)
        v = getAttrWithFallback(font.info, "openTypeOS2StrikeoutPosition")
        if v is None:
            v = xHeight * 0.6 if xHeight else unitsPerEm * 0.22
        os2.yStrikeoutPosition = round(v)

        # family class
        ibmFontClass, ibmFontSubclass = getAttrWithFallback(
            font.info, "openTypeOS2FamilyClass")
        os2.sFamilyClass = (ibmFontClass << 8) + ibmFontSubclass
        # panose
        data = getAttrWithFallback(font.info, "openTypeOS2Panose")
        panose = Panose()
        panose.bFamilyType = data[0]
        panose.bSerifStyle = data[1]
        panose.bWeight = data[2]
        panose.bProportion = data[3]
        panose.bContrast = data[4]