def METHOD_NAME() -> pd.DataFrame:
  """Returns the codename to version mapping"""
  with request.urlopen(DEBIAN_RELEASE_VERSIONS_URL) as csv:
    df = pd.read_csv(csv, dtype=str)
    # `series` appears to be `codename` but with no caps
    df['sources'] = ''
    df.dropna(subset=['release'], inplace=True)
    codename_to_version = df.set_index('series')
  return codename_to_version