<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def put(self, entity):
 """Registers entity to put to datastore. Args: entity: an entity or model instance to put. """

    actual_entity = _normalize_entity(entity)
    if actual_entity is None:
      return self.ndb_put(entity)
    self.puts.append(actual_entity)