@classmethod
  def _ConstructAccessTokenGuessId(cls, identity_type, user_id):
    if identity_type == 'Email':
      return Guess.ConstructGuessId('em', user_id)

    assert identity_type == 'Phone', identity_type
    return Guess.ConstructGuessId('ph', user_id)
New ChainMap or subclass with a new copy of maps[0] and refs to maps[1:]
dataset/ETHPy150Open viewfinderco/viewfinder/backend/db/identity.py/Identity._ConstructAccessTokenGuessId--crossover with--dataset/ETHPy150Open ionelmc/python-aspectlib/src/aspectlib/py2chainmap.py/ChainMap.copy