'Mutates block_structure based on the given usage_info.'

def transform(self, usage_info, block_structure):

    for block_key in block_structure.post_order_traversal():
        if (block_structure.get_xblock_field(block_key, 'category') not in self.requested_student_view_data):
            block_structure.remove_transformer_block_field(block_key, self, self.STUDENT_VIEW_DATA)
