docs: def discover_datasource_columns(datastore_str, datasource_id):
      """ Loop through the datastore's datasources to find
      the datasource identified by datasource_id, return
      the matching datasource's columns. """
      datastore = DataStore(datastore_str)
      datasource = datastore.get_datasource(datasource_id)
      if datasource.type != "RASTER":
          return datasource.list_columns()
      else:
          return []