code: def load(self, dataset_keys, previous_datasets=None):
          
          all_datasets = previous_datasets or DatasetDict()
          datasets = DatasetDict()
  
          # Include coordinates in the list of datasets to load
          dsids = [self.get_dataset_key(ds_key) for ds_key in dataset_keys]
          coordinates = self._get_coordinates_for_dataset_keys(dsids)
          all_dsids = list(set().union(*coordinates.values())) + dsids
  
          for dsid in all_dsids:
              if dsid in all_datasets:
                  continue
              coords = [all_datasets.get(cid, None)
                        for cid in coordinates.get(dsid, [])]
              ds = self._load_dataset_with_area(dsid, coords)
              if ds is not None:
                  all_datasets[dsid] = ds
                  if dsid in dsids:
                      datasets[dsid] = ds
          self._load_ancillary_variables(all_datasets)
  
          return datasets
docs: Load `dataset_keys`.
  
          If `previous_datasets` is provided, do not reload those.