efines the parameters of the sinh/cosh pseudo-differential
    operator.
period : float, optional
    The period of the sequence x. Default is 2*pi.

Notes
-----
``sc_diff(cs_diff(x,a,b),b,a) == x``
For even ``len(x)``, the Nyquist mode of x is taken as zero.

Ú
sc_diff_cacher