@classmethod
def get_block_aggregators(cls, block_structure, block_key):
    """
        Return the aggregators which contain this block.

        Arguments:
            block_structure: a BlockStructure instance
            block_key: the key of the block whose aggregators we want
        Returns:
            aggregators: list or None

        """
    return block_structure.get_transformer_block_field(block_key, cls, cls.
        AGGREGATORS)
