MAINT: address a review comment

Author: ev-br

torch_np/_funcs_impl.py

@@ -8,6 +8,7 @@
 from __future__ import annotations
 
 import builtins
+import itertools
 import math
 import operator
 from typing import Optional, Sequence
@@ -1280,7 +1281,9 @@ def einsum(*operands, out=None, optimize=False, **kwargs):
         # recombine operands
         sublists = operands[1::2]
         sublistout = (operands[-1],) if len(operands) % 2 == 1 else ()
-        operands = builtins.sum((_ for _ in zip(tensors, sublists)), ()) + sublistout
+        operands = list(itertools.chain(*zip(tensors, sublists)))
+        if len(operands) % 2 == 1:
+            operands.append(sublistout)
 
         result = torch.einsum(*operands)
     else: