torch.Tensor.index_copy_
Tensor.index_copy_(dim, index, tensor) -> Tensor
Copies the elements of "tensor" into the "self" tensor by selecting
   the indices in the order given in "index". For example, if "dim ==
   0" and "index[i] == j", then the "i"th row of "tensor" is copied to
   the "j"th row of "self".
The "dim"th dimension of "tensor" must have the same size as the
   length of "index" (which must be a vector), and all other
   dimensions must match "self", or an error will be raised.
Note:
 If "index" contains duplicate entries, multiple elements from
 "tensor" will be copied to the same index of "self". The result
 is nondeterministic since it depends on which copy occurs last.

Parameters:
      * dim (int) -- dimension along which to index
  * **index** (*LongTensor*) -- indices of "tensor" to select from

  * **tensor** (*Tensor*) -- the tensor containing values to copy

Example:
  >>> x = torch.zeros(5, 3)
