torch.atan
torch.atan(input, *, out=None) -> Tensor
Returns a new tensor with the arctangent of the elements of
   "input".
  \text{out}_{i} = \tan^{-1}(\text{input}_{i})

Parameters:
      input (Tensor) -- the input tensor.
Keyword Arguments:
      out (Tensor, optional) -- the output tensor.
Example:
  >>> a = torch.randn(4)
  >>> a
  tensor([ 0.2341,  0.2539, -0.6256, -0.6448])
  >>> torch.atan(a)
  tensor([ 0.2299,  0.2487, -0.5591, -0.5727])
