How to use the ufo2ft.featureWriters.ast.MarkClass function in ufo2ft

markClasses[className] = markClass
        else:
            if accentName in markClass.glyphs:
                mcdef = markClass.glyphs[accentName]
                if cls._anchorsAreEqual(anchor, mcdef.anchor):
                    logger.debug(
                        "Glyph %s already defined in markClass @%s",
                        accentName,
                        className,
                    )
                    return None
                else:
                    # same accent glyph defined with different anchors for the
                    # same markClass; make a new unique markClass definition
                    newClassName = ast.makeFeaClassName(className, markClasses)
                    markClass = ast.MarkClass(newClassName)
                    markClasses[newClassName] = markClass
        mcdef = ast.MarkClassDefinition(markClass, anchor, glyphs)
        markClass.addDefinition(mcdef)
        return mcdef

markClasses[className] = markClass
        else:
            if glyphName in markClass.glyphs:
                mcdef = markClass.glyphs[glyphName]
                if self._anchorsAreEqual(anchor, mcdef.anchor):
                    self.log.debug(
                        "Glyph %s already defined in markClass @%s",
                        glyphName,
                        className,
                    )
                    return None
                else:
                    # same mark glyph defined with different anchors for the
                    # same markClass; make a new unique markClass definition
                    newClassName = ast.makeFeaClassName(className, markClasses)
                    markClass = ast.MarkClass(newClassName)
                    markClasses[newClassName] = markClass
        glyphName = ast.GlyphName(glyphName)
        mcdef = ast.MarkClassDefinition(markClass, anchor, glyphName)
        markClass.addDefinition(mcdef)
        return mcdef

def _makeMarkClass(cls, markClasses, accentName, x, y, className):
        """ Make a MarkClassDefinition statement given the accent name,
        position, class name, and pre-existing mark classes.
        Return None if a mark class with the same name and anchor already
        exists. Or create new mark class with unique name when different.
        """
        glyphs = ast.GlyphName(accentName)
        anchor = cls._makeAnchorFormatA(x, y)
        className = ast.makeFeaClassName(className)
        markClass = markClasses.get(className)
        if markClass is None:
            markClass = ast.MarkClass(className)
            markClasses[className] = markClass
        else:
            if accentName in markClass.glyphs:
                mcdef = markClass.glyphs[accentName]
                if cls._anchorsAreEqual(anchor, mcdef.anchor):
                    logger.debug(
                        "Glyph %s already defined in markClass @%s",
                        accentName,
                        className,
                    )
                    return None
                else:
                    # same accent glyph defined with different anchors for the
                    # same markClass; make a new unique markClass definition
                    newClassName = ast.makeFeaClassName(className, markClasses)
                    markClass = ast.MarkClass(newClassName)

def _defineMarkClass(self, glyphName, x, y, className, markClasses):
        anchor = ast.Anchor(x=otRound(x), y=otRound(y))
        markClass = markClasses.get(className)
        if markClass is None:
            markClass = ast.MarkClass(className)
            markClasses[className] = markClass
        else:
            if glyphName in markClass.glyphs:
                mcdef = markClass.glyphs[glyphName]
                if self._anchorsAreEqual(anchor, mcdef.anchor):
                    self.log.debug(
                        "Glyph %s already defined in markClass @%s",
                        glyphName,
                        className,
                    )
                    return None
                else:
                    # same mark glyph defined with different anchors for the
                    # same markClass; make a new unique markClass definition
                    newClassName = ast.makeFeaClassName(className, markClasses)
                    markClass = ast.MarkClass(newClassName)