docs: def songs(self):
          """
          iterator over artist's songs as :class:`Song` objects
          """
          if self._songs is None:
              self._songs = [Song.from_response(song, self._connection) for song in
                             self._connection.request(
                                 'artistGetArtistSongs',
                                 {'artistID': self.id},
                                 self._connection.header('artistGetArtistSongs'))[1]]
          return iter(self._songs)