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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def backup_file(*, file, host):
 """ Perform backup action on set driver :param file: Name of the file to be used by the driver :param host: Corresponding host name associated with file """

    if _driver:
        log.msg_debug("[{driver}] Backing up file '{file}'"
                      .format(driver=_driver.get_name(), file=file))
        _driver.backup_file(file=file, host=host)