code: def run(self):
          
          w = self.output().open('w')
          for user in range(self.data_size):
              track = int(random.random() * self.data_size)
              w.write('%d\\%d\\%f' % (user, track, 1.0))
          w.close()
docs: Generates :py:attr:`~.UserItemMatrix.data_size` elements.
          Writes this data in \\ separated value format into the target :py:func:`~/.UserItemMatrix.output`.
  
          The data has the following elements:
  
          * `user` is the default Elasticsearch id field,
          * `track`: the text,
          * `rating`: the day when the data was created.