docs: def is_email(data):
      """
      Check if given data string is an email.
  
      Usage::
  
          >>> is_email("john.doe@domain.com")
          True
          >>> is_email("john.doe:domain.com")
          False
  
      :param data: Data to check.
      :type data: unicode
      :return: Is email.
      :rtype: bool
      """
  
      if re.match(r"[\w.%+-]+@[\w.]+\.[a-zA-Z]{2,4}", data):
          LOGGER.debug("> {0}' is matched as email.".format(data))
          return True
      else:
          LOGGER.debug("> {0}' is not matched as email.".format(data))
          return False