<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set(self, section, val, data):
 """Add a setting to the config `section` (mandatory) (string) the section name in the config E.g. `"agent"` `val` (mandatory) (string) the section name in the config E.g. `"host"` `data` (mandatory) (as appropriate) the new value for the `val` """

        val = val.lower()
        if section in self.__config:
            # logger.debug('set %s %s = %s', section, val, data)
            self.__config[section][val] = data