Creates a frame and writes it to disk.

    Args:
      arrays: a list of np arrays. Use the "custom" option in the client.
      frame: a 2D np array. This way the plugin can be used for video of any
             kind, not just the visualization that comes with the plugin.

             frame can also be a function, which only is evaluated when the
             "frame" option is selected by the client.

def update(self, session, arrays=None, frame=None):
    '''Creates a frame and writes it to disk.

    Args:
      arrays: a list of np arrays. Use the "custom" option in the client.
      frame: a 2D np array. This way the plugin can be used for video of any
             kind, not just the visualization that comes with the plugin.

             frame can also be a function, which only is evaluated when the
             "frame" option is selected by the client.
    '''
    new_config = self._get_config()

    if self._enough_time_has_passed(self.previous_config['FPS']):
      self.visualizer.update(new_config)
      self.last_update_time = time.time()
      final_image = self._update_frame(session, arrays, frame, new_config)
      self._update_recording(final_image, new_config)