code: def _load_dataset(dsid, ds_info, file_handlers, dim='y'):
          
          slice_list = []
          failure = True
          for fh in file_handlers:
              try:
                  projectable = fh.get_dataset(dsid, ds_info)
                  if projectable is not None:
                      slice_list.append(projectable)
                      failure = False
              except KeyError:
                  logger.warning("Failed to load {} from {}".format(dsid, fh),
                                 exc_info=True)
  
          if failure:
              raise KeyError(
                  "Could not load {} from any provided files".format(dsid))
  
          if dim not in slice_list[0].dims:
              return slice_list[0]
          res = xr.concat(slice_list, dim=dim)
  
          combined_info = file_handlers[0].combine_info(
              [p.attrs for p in slice_list])
  
          res.attrs = combined_info
          return res
docs: Load only a piece of the dataset.