code: def read(self, output_tile, **kwargs):
          
          path = self.get_path(output_tile)
          try:
              with fiona.open(path, "r") as src:
                  return list(src)
          except DriverError as e:
              for i in ("does not exist in the file system", "No such file or directory"):
                  if i in str(e):
                      return self.empty(output_tile)
              else:
                  raise
docs: Read existing process output.
  
          Parameters
          ----------
          output_tile : ``BufferedTile``
              must be member of output ``TilePyramid``
  
          Returns
          -------
          process output : list