def allpass(self, frequency, width_q=<NUM_LIT>):
if not is_number(frequency) or frequency <= <NUM_LIT:0>:<EOL><INDENT>raise ValueError("<STR_LIT>")<EOL><DEDENT>if not is_number(width_q) or width_q <= <NUM_LIT:0>:<EOL><INDENT>raise ValueError("<STR_LIT>")<EOL><DEDENT>effect_args = [<EOL>'<STR_LIT>', '<STR_LIT>'.format(frequency), '<STR_LIT>'.format(width_q)<EOL>]<EOL>self.effects.extend(effect_args)<EOL>self.effects_log.append('<STR_LIT>')<EOL>return self<EOL>
Apply a two-pole all-pass filter. An all-pass filter changes the
        audio’s frequency to phase relationship without changing its frequency
        to amplitude relationship. The filter is described in detail in at
        http://musicdsp.org/files/Audio-EQ-Cookbook.txt

        Parameters
        ----------
        frequency : float
            The filter's center frequency in Hz.
        width_q : float, default=2.0
            The filter's width as a Q-factor.

        See Also
        --------
        equalizer, highpass, lowpass, sinc