<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _conversion(self, input_signal, vad_file):
 """ Converts an external VAD to follow the Spear convention. Energy is used in order to avoind out-of-bound array indexes. """

    
    e = bob.ap.Energy(rate_wavsample[0], self.win_length_ms, self.win_shift_ms)
    energy_array = e(rate_wavsample[1])
    labels = self.use_existing_vad(energy_array, vad_file)
    
    return labels