def _apply_predicate_to_row_groups(self, dataset, row_groups, predicate):
        """Filters the list of row group indexes using rowgroup selector object. Returns a modified list of rowgroup
        indexes and a list of worker_predicate: predicates that could not be applied at this level
        (parquet partitioning)."""

        if predicate:
            if not isinstance(predicate, PredicateBase):
                raise ValueError('predicate parameter is expected to be derived from PredicateBase')
            predicate_fields = predicate.get_fields()

            partition_names = dataset.partitions.partition_names if dataset.partitions else set()
            if set(predicate_fields) == partition_names:
                assert len(partition_names) == 1, \
                    'Datasets with only a single partition level supported at the moment'

                filtered_row_group_indexes = []
                for piece_index, piece in enumerate(row_groups):
                    partition_name, partition_index = piece.partition_keys[0]
                    partition_value = dataset.partitions[0].keys[partition_index]

                    # Convert partition value to correct type per the schema
                    partition_value = self.schema.fields[partition_name].numpy_dtype(partition_value)
                    if predicate.do_include({partition_name: partition_value}):
                        filtered_row_group_indexes.append(piece_index)
                worker_predicate = None
            else:
                filtered_row_group_indexes = list(range(len(row_groups)))
                worker_predicate = predicate

        else:
            filtered_row_group_indexes = list(range(len(row_groups)))
            worker_predicate = None
        return filtered_row_group_indexes, worker_predicate
Filters the list of row group indexes using rowgroup selector object. Returns a modified list of rowgroup
        indexes and a list of worker_predicate: predicates that could not be applied at this level
        (parquet partitioning).
petastorm/reader.py