'Trims a given number of steps from the end of the sequence.'

def _trim_steps(self, num_steps):

    steps_trimmed = 0
    for i in reversed(range(len(self._events))):
        if (self._events[i].event_type == PolyphonicEvent.STEP_END):
            if (steps_trimmed == num_steps):
                del self._events[(i + 1):]
                break
            steps_trimmed += 1
        elif (i == 0):
            self._events = [PolyphonicEvent(event_type=PolyphonicEvent.START, pitch=None)]
            break
