'Print out the value of ``self._threads`` or ``self._filtered_hreads``'

def _show_threads(self, filter=False, show_thread_readings=False):

    threads = (self._filtered_threads if filter else self._threads)
    for tid in sorted(threads):
        if show_thread_readings:
            readings = [self._readings[rid.split('-')[0]][rid] for rid in self._threads[tid]]
            try:
                thread_reading = (':    %s' % self._reading_command.combine_readings(readings).normalize())
            except Exception as e:
                thread_reading = (':    INVALID:    %s' % e.__class__.__name__)
        else:
            thread_reading = ''
        print(('%s:' % tid), self._threads[tid], thread_reading)
