Remove NONSPEECH fragments from list if needed,
        and set HEAD/TAIL begin/end.

def _smooth_fragment_list(self, real_wave_mfcc_audio_length, ns_string):
        """
        Remove NONSPEECH fragments from list if needed,
        and set HEAD/TAIL begin/end.
        """
        self.log(u"Called _smooth_fragment_list")
        self.smflist[0].begin = TimeValue("0.000")
        self.smflist[-1].end = real_wave_mfcc_audio_length
        if ns_string in [None, gc.PPV_TASK_ADJUST_BOUNDARY_NONSPEECH_REMOVE]:
            self.log(u"Remove all NONSPEECH fragments")
            self.smflist.remove_nonspeech_fragments(zero_length_only=False)
        else:
            self.log(u"Remove NONSPEECH fragments with zero length only")
            self.smflist.remove_nonspeech_fragments(zero_length_only=True)