tensor types.
  * **requires_grad** (*bool**, **optional*) -- If autograd should
    record operations on the returned tensor. Default: "False".

Return type:
      Tensor
Examples:
  >>> # Generates a symmetric exponential window of size 10 and with a decay value of 1.0.
  >>> # The center will be at (M - 1) / 2, where M is 10.
  >>> torch.signal.windows.exponential(10)
  tensor([0.0111, 0.0302, 0.0821, 0.2231, 0.6065, 0.6065, 0.2231, 0.0821, 0.0302, 0.0111])

  >>> # Generates a periodic exponential window and decay factor equal to .5
  >>> torch.signal.windows.exponential(10, sym=False,tau=.5)
  tensor([4.5400e-05, 3.3546e-04, 2.4788e-03, 1.8316e-02, 1.3534e-01, 1.0000e+00, 1.3534e-01, 1.8316e-02, 2.4788e-03, 3.3546e-04])
