How to use the gftools.util.google_fonts.Metadata function in gftools

def main(argv):
  if len(argv) != 2 or not os.path.isdir(argv[1]):
    sys.exit('Must have one argument, a directory containing font files.')

  sys.stderr = open(os.devnull, 'w')
  dirpath = argv[1]
  result = True
  files = []
  for font in fonts.Metadata(dirpath).fonts:
    files.append(os.path.join(dirpath, font.filename))
  for subset in fonts.Metadata(dirpath).subsets:
    if subset == 'menu':
      continue
    (file1, file2, diff_size)  = _LeastSimilarCoverage(files, subset)
    if diff_size > FLAGS.max_diff_cps:
      print('%s coverage for %s failed' % (dirpath, subset))
      print('Difference of codepoints between %s & %s is %d' % (
          file1, file2, diff_size))
      result = False

  if result:
    print('%s passed subset coverage' % (dirpath))

def CompareDirs(font1, font2):
  """Compares fonts by assuming font1/2 are dirs containing METADATA.pb."""

  m1 = fonts.Metadata(font1)
  m2 = fonts.Metadata(font2)

  subsets_to_compare = fonts.UniqueSort(m1.subsets, m2.subsets)
  subsets_to_compare.remove('menu')
  subsets_to_compare.append('all')

  font_filename1 = os.path.join(font1, fonts.RegularWeight(m1))
  font_filename2 = os.path.join(font2, fonts.RegularWeight(m2))

  if FLAGS.diff_coverage:
    print('Subset Coverage Change (codepoints)')
    for subset in subsets_to_compare:
      DiffCoverage(font_filename1, font_filename2, subset)

  print(CompareSize(font_filename1, font_filename2))

def _SanityCheck(path):
  """Runs various sanity checks on the font family under path.

  Args:
    path: A directory containing a METADATA.pb file.
  Returns:
    A list of ResultMessageTuple's.
  """
  try:
    fonts.Metadata(path)
  except ValueError as e:
    return [_SadResult('Bad METADATA.pb: ' + e.message, path)]

  results = []
  if FLAGS.check_metadata:
    results.extend(_CheckLicense(path))
    results.extend(_CheckNameMatching(path))

  if FLAGS.check_font:
    results.extend(_CheckFontInternalValues(path))

  return results

def _CheckLicense(path):
  """Verifies that METADATA.pb license is correct under path.

  Assumes path is of the form ...///METADATA.pb.

  Args:
    path: A directory containing a METADATA.pb file.
  Returns:
    A list with one ResultMessageTuple. If happy, license is good.
  """
  metadata = fonts.Metadata(path)
  lic = metadata.license
  lic_dir = os.path.basename(os.path.dirname(path))

  # We use /apache for the license Apache2
  if lic_dir == 'apache':
    lic_dir += '2'

  result = _HappyResult('License consistantly %s' % lic, path)
  # if we were Python 3 we'd use casefold(); this will suffice
  if lic_dir.lower() != lic.lower():
    result = _SadResult('Dir license != METADATA license: %s != %s' %
                        (lic_dir, lic), path)

  return [result]

def _CheckNameMatching(path):
  """Verifies the various name fields in the METADATA.pb file are sane.

  Args:
    path: A directory containing a METADATA.pb file.
  Returns:
    A list of ResultMessageTuple, one per validation performed.
  """
  results = []
  metadata = fonts.Metadata(path)
  name = metadata.name

  for font in metadata.fonts:
    # We assume style/weight is correct in METADATA
    style = font.style
    weight = font.weight
    values = [('name', name, font.name), ('filename', fonts.FilenameFor(
        name, style, weight, '.ttf'), font.filename),
              ('postScriptName', fonts.FilenameFor(name, style, weight),
               font.post_script_name), ('fullName', fonts.FullnameFor(
                   name, style, weight), font.full_name)]

    for (key, expected, actual) in values:
      if expected != actual:
        results.append(
            _SadResult('%s METADATA %s/%d %s expected %s, got %s' %

def _CheckFontInternalValues(path):
  """Validates fonts internal metadata matches METADATA.pb values.

  In particular, checks 'OS/2' {usWeightClass, fsSelection, fsType} and 'name'
  {fullName, postScriptName} values.

  Args:
    path: A directory containing a METADATA.pb file.
  Returns:
    A list of ResultMessageTuple, one per validation performed.
  """
  results = []
  metadata = fonts.Metadata(path)
  name = metadata.name

  for font in metadata.fonts:
    font_file = font.filename
    with contextlib.closing(ttLib.TTFont(os.path.join(path, font_file))) as ttf:
      results.extend(_CheckFontOS2Values(path, font, ttf))
      results.extend(_CheckFontNameValues(path, name, font, ttf))
      results.extend(_CheckLSB0ForEmptyGlyphs(path, font, ttf))

  return results

def CompareDirs(font1, font2):
  """Compares fonts by assuming font1/2 are dirs containing METADATA.pb."""

  m1 = fonts.Metadata(font1)
  m2 = fonts.Metadata(font2)

  subsets_to_compare = fonts.UniqueSort(m1.subsets, m2.subsets)
  subsets_to_compare.remove('menu')
  subsets_to_compare.append('all')

  font_filename1 = os.path.join(font1, fonts.RegularWeight(m1))
  font_filename2 = os.path.join(font2, fonts.RegularWeight(m2))

  if FLAGS.diff_coverage:
    print('Subset Coverage Change (codepoints)')
    for subset in subsets_to_compare:
      DiffCoverage(font_filename1, font_filename2, subset)

  print(CompareSize(font_filename1, font_filename2))