dim: (int or tuple of ints) the dimension or dimensions to reduce.
keepdim: (bool) whether the output tensor has dim retained or not.
logsumexp(input, dim, keepdim=False, out=NULL)
Returns the log of summed exponentials of each row of the input
tensor in the given dimension dim. The computation is numerically stabilized.
For summation index j given by dim and other indices i, the result is
\mboxlogsumexp(x)i=logj∑exp(xij)
If keepdim is TRUE, the output tensor is of the same size as input except in the dimension(s) dim where it is of size 1. Otherwise, dim is squeezed (see torch_squeeze), resulting in the output tensor having 1 (or len(dim)) fewer dimension(s).