def METHOD_NAME(self):
    """
    Retrieves the cause of the previous reboot
    Returns:
        A tuple (string, string) where the first element is a string
        containing the cause of the previous reboot. This string must be
        one of the predefined strings in this class. If the first string
        is "REBOOT_CAUSE_HARDWARE_OTHER", the second string can be used
        to pass a description of the reboot cause.
    """
    if os.path.exists(REBOOT_CAUSE_FILE):
        with open(REBOOT_CAUSE_FILE) as reboot_cause_file:
            reboot_cause = reboot_cause_file.readline()
        if re.search(r'User issued', reboot_cause) is None:
            return (self.REBOOT_CAUSE_POWER_LOSS, None)
        else:
            return (self.REBOOT_CAUSE_NON_HARDWARE, None)
    else:
        return (self.REBOOT_CAUSE_POWER_LOSS, None)