input : array_like
shift : float or sequence
The size of the box used for filtering.
If a float, shift is the same for all axes. If a sequence, shift
has to contain one value for each axis.
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 shifting the input is placed in this array.
None is returned in this case.