code: def get_possible_initializer_keys(cls, use_peepholes=False,
                                      use_projection=False):
      
  
      possible_keys = cls.POSSIBLE_INITIALIZER_KEYS.copy()
      if not use_peepholes:
        possible_keys.difference_update(
            {cls.W_F_DIAG, cls.W_I_DIAG, cls.W_O_DIAG})
      if not use_projection:
        possible_keys.difference_update({cls.W_H_PROJECTION})
      return possible_keys
docs: Returns the keys the dictionary of variable initializers may contain.
  
      The set of all possible initializer keys are:
        w_gates:  weight for gates
        b_gates:  bias of gates
        w_f_diag: weight for prev_cell -> forget gate peephole
        w_i_diag: weight for prev_cell -> input gate peephole
        w_o_diag: weight for prev_cell -> output gate peephole
  
      Args:
        cls:The class.
        use_peepholes: Boolean that indicates whether peephole connections are
          used.
        use_projection: Boolean that indicates whether a recurrent projection
          layer is used.
  
      Returns:
        Set with strings corresponding to the strings that may be passed to the
          constructor.