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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def com_google_fonts_check_family_equal_font_versions(ttFonts):
 """Make sure all font files have the same version value."""

  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."