def ListFeatures(font):
  """List features for specified font. Table assumed structured like GPS/GSUB.

  Args:
    font: a TTFont.
  Returns:
    List of 3-tuples of ('GPOS', tag, name) of the features in the font.
  """
  results = []
  for tbl in ["GPOS", "GSUB"]:
    if tbl in font.keys():
      results += [
        (tbl,
         f.FeatureTag,
         "lookups: [{}]".format(", ".join(map(str, f.Feature.LookupListIndex)))
        ) for f in font[tbl].table.FeatureList.FeatureRecord
      ]
  return results