input : array_like
sigma : float or sequence
The sigma of the Gaussian kernel. If a float, sigma is the same for
all axes. If a sequence, sigma has to contain one value for each
n : int, optional
If n is negative (default), then the input is assumed to be the
result of a complex fft.
If n is larger than or equal to zero, the input is assumed to be the
result of a real fft, and n gives the length of the array before
transformation along the real transform direction.
axis : int, optional
The axis of the real transform.
output : ndarray, optional
If given, the result of filtering the input is placed in this array.
None is returned in this case.