ngth *NFFT*.  To create window vectors see
    `.window_hanning`, `.window_none`, `numpy.blackman`, `numpy.hamming`,
    `numpy.bartlett`, `scipy.signal`, `scipy.signal.get_window`, etc.  If a
    function is passed as the argument, it must take a data segment as an
    argument and return the windowed version of the segment.

sides : {'default', 'onesided', 'twosided'}, optional
    Which sides of the spectrum to return. 'default' is one-sided for real
    data and two-sided for complex data. 'onesided' forces the return of a
    one-sided spectrum, while 'twosided' forces two-sided.a