'Deletes the given transformer\'s entire data dict for the
block identified by the given usage_key.
Arguments:
usage_key (UsageKey) - Usage key of the block whose
transformer data is to be deleted.
transformer (BlockStructureTransformer) - The transformer
whose data entry is to be deleted.'

def remove_transformer_block_field(self, usage_key, transformer, key):

    try:
        transformer_block_data = self.get_transformer_block_data(usage_key, transformer)
        delattr(transformer_block_data, key)
    except (AttributeError, KeyError):
        pass
