code: def com_google_fonts_check_family_equal_font_versions(ttFonts):
    
    all_detected_versions = []
    fontfile_versions = {}
    for ttFont in ttFonts:
      v = ttFont['head'].fontRevision
      fontfile_versions[ttFont] = v
  
      if v not in all_detected_versions:
        all_detected_versions.append(v)
    if len(all_detected_versions) != 1:
      versions_list = ""
      for v in fontfile_versions.keys():
        versions_list += "* {}: {}\n".format(v.reader.file.name,
                                             fontfile_versions[v])
      yield WARN, ("version info differs among font"
                   " files of the same font project.\n"
                   "These were the version values found:\n"
                   "{}").format(versions_list)
    else:
      yield PASS, "All font files have the same version."
docs: Make sure all font files have the same version value.