Duplicate line of code when computing _backward_idempotent

[linyuhongg]

In variable.py, the operation + calls _backward_idempotent for autograd, however, this function has a duplicate line of code line 349 and line 355 are the same code resulting in duplicate gradients for variables involved in the Function '+'.

[linyuhongg]

Perhaps it was meant to work with _reduce_meta? However, it seems like if its not defined, it results in duplicate gradients when using +