code: def tiles_exist(self, process_tile=None, output_tile=None):
          
          if process_tile and output_tile:
              raise ValueError("just one of 'process_tile' and 'output_tile' allowed")
          if process_tile:
              return any(
                  path_exists(self.get_path(tile))
                  for tile in self.pyramid.intersecting(process_tile)
              )
          if output_tile:
              return path_exists(self.get_path(output_tile))
docs: Check whether output tiles of a tile (either process or output) exists.
  
          Parameters
          ----------
          process_tile : ``BufferedTile``
              must be member of process ``TilePyramid``
          output_tile : ``BufferedTile``
              must be member of output ``TilePyramid``
  
          Returns
          -------
          exists : bool