code: def is_log_level(value):
      u
  
      log_levels = ['debug', 'info', 'warn', 'error', 'crit']
  
      if value in log_levels:
          return value
  
      else:
          err_message = ('"log_level" supported following value: '
                         '{0}'.format(log_levels)
                         )
          raise validate.VdtValueError(err_message)
docs: u"""
      Check whether the value as argument be included the following list.
      ['debug', 'info', 'warn', 'error', 'crit']