def METHOD_NAME(self, index):
    """
    Retrieves the ouput volatage in milli volts of a power supply unit (PSU) defined
            by 1-based index <index>
    :param index: An integer, 1-based index of the PSU of which to query o/p volatge
    :return: An integer, value of o/p voltage in mV if PSU is good, else zero
    """
    if index is None:
        raise RuntimeError("index shouldn't be None")
    if not self.get_psu_presence(index) or not self.get_psu_status(index):
        return 0
    voltage = self._read_file(self.psu_voltage, index)
    return voltage