torch.Tensor.masked_scatter_
Tensor.masked_scatter_(mask, source)
Copies elements from "source" into "self" tensor at positions where
   the "mask" is True. The shape of "mask" must be broadcastable with
   the shape of the underlying tensor. The "source" should have at
   least as many elements as the number of ones in "mask"
Parameters:
      * mask (BoolTensor) -- the boolean mask
  * **source** (*Tensor*) -- the tensor to copy from

Note:
 The "mask" operates on the "self" tensor, not on the given
 "source" tensor.
