code: def set_screen(self, screen, overwrite=False):
          
          if self._screen is not None and not overwrite:
              raise ValueError(
                  "set_screen() called with overwrite=False and screen already "
                  "set.\n"
                  "If you want to apply multiple filters as a screen use "
                  "set_screen(filter1 & filter2 & ...).\n"
                  "If you want to replace the previous screen with a new one, "
                  "use set_screen(new_filter, overwrite=True)."
              )
          self._screen = screen
docs: Set a screen on this Pipeline.
  
          Parameters
          ----------
          filter : zipline.pipeline.Filter
              The filter to apply as a screen.
          overwrite : bool
              Whether to overwrite any existing screen.  If overwrite is False
              and self.screen is not None, we raise an error.