def overlap(self, a_blocks, b) :
        b_index = self.block_index[b]
        b_index_get = b_index.get
        cover_b = self.cover[b]
        null_set = set()
        for first, second in a_blocks:
            seen_y = set()
            for record_id in first:
                b_blocks = b_index_get(record_id, null_set)
                for y in b_blocks:
                    if seen_y not in y :
                        yield first & cover_b[y][0], second & cover_b[y][1]
                    seen_y |= b_blocks
dataset/ETHPy150Open datamade/dedupe/dedupe/training.py/RecordLinkCompounder.overlap/swapped operands of `not in`