[skip ci] Fix mishards query result reduce error (#3256)

Signed-off-by: yinghao.zou <yinghao.zou@zilliz.com>

Author: BossZou

shards/mishards/service_handler.py

@@ -27,7 +27,8 @@ def __init__(self, tracer, router, max_workers=multiprocessing.cpu_count(), **kw
         self.max_workers = max_workers
 
     def _reduce(self, source_ids, ids, source_diss, diss, k, reverse):
-        sort_f = lambda x, y: x >= y if reverse else lambda x, y: x <= y
+        sort_f = (lambda x, y: x >= y) if reverse else (lambda x, y: x <= y)
+
         if sort_f(source_diss[k - 1], diss[0]):
             return source_ids, source_diss
         if sort_f(diss[k - 1], source_diss[0]):