code: def antennas_missing_locations(user, Method=None):
      
      unique_antennas = set([record.position.antenna for record in user.records
                             if record.position.antenna is not None])
      return sum([1 for antenna in unique_antennas if user.antennas.get(antenna) is None])
docs: Return the number of antennas missing locations in the records of a given user.