Returns
        -------
        spectrum : 1-D array
            The values for the phase spectrum in radians (real valued).

        freqs : 1-D array
            The frequencies corresponding to the elements in *spectrum*.

        line : `~matplotlib.lines.Line2D`
            The line created by this function.

        Other Parameters
        ----------------
        data : indexable object, optional
            DATA_PARAMETER_PLACEHOLDER

        **kwargs
            Keyword arguments control the `.Line2D` properties:

            %(Line2D:kwdoc)s

        See Also
        --------
        magnitude_spectrum
            Plots the magnitudes of the corresponding frequencies.
        angle_spectrum
            Plots the wrapped version of this function.
        specgram
            Can plot the phase spectrum of segments within the signal in a
            colormap.
        Nr