OUTPUT PARQUET METADATA COLUMNS
        :param path: FOR INTERNAL USE
        :return: LIST OF SchemaElement

def get_parquet_metadata(
        self,
        path='.'
    ):
        """
        OUTPUT PARQUET METADATA COLUMNS
        :param path: FOR INTERNAL USE
        :return: LIST OF SchemaElement
        """
        children = []
        for name, child_schema in sort_using_key(self.more.items(), lambda p: p[0]):
            children.extend(child_schema.get_parquet_metadata(concat_field(path, name)))

        if path == '.':
            return children
        else:
            self.element.num_children = len(children)
            return [self.element] + children