code: def _fire(self, layers, the_plot):
      
      # We don't fire if another Marauder fired a bolt just now.
      if the_plot.get('last_marauder_shot') == the_plot.frame: return
      the_plot['last_marauder_shot'] = the_plot.frame
      # Which Marauder should fire the laser bolt?
      col = np.random.choice(np.nonzero(layers['X'].sum(axis=0))[0])
      row = np.nonzero(layers['X'][:, col])[0][-1] + 1
      # Move ourselves just below that Marauder.
      self._teleport((row, col))
docs: Launches a new bolt from a random Marauder.