Resets the value of config item to its default value.

def reset(self):
        """
        Resets the value of config item to its default value.
        """
        old_value = self._value
        old_raw_str_value = self.raw_str_value

        self._value = not_set
        self.raw_str_value = not_set

        new_value = self._value

        if old_value is not_set:
            # Nothing to report
            return

        if self.section:
            self.section.dispatch_event(
                self.section.hooks.item_value_changed,
                item=self,
                old_value=old_value,
                new_value=new_value,
                old_raw_str_value=old_raw_str_value,
                new_raw_str_value=self.raw_str_value,
            )