code: def set_to_default(section, key):
      
      section[key] = section.default_values.get(key, section[key])
docs: Set the value of the given seciton and key to default
  
      :param section: the section of a configspec
      :type section: section
      :param key: a key of the section
      :type key: str
      :returns: None
      :raises: None