def dump_conf(self, config_pathname=None):
        """write a config file to the pathname specified in the parameter.  The
        file extention determines the type of file written and must match a
        registered type.

        parameters:
            config_pathname - the full path and filename of the target config
                               file."""

        if not config_pathname:
            config_pathname = self._get_option('admin.dump_conf').value

        opener = functools.partial(open, config_pathname, 'w')
        config_file_type = os.path.splitext(config_pathname)[1][1:]

        skip_keys = [
            k for (k, v)
            in six.iteritems(self.option_definitions)
            if isinstance(v, Option) and v.exclude_from_dump_conf
        ]

        self.write_conf(config_file_type, opener, skip_keys=skip_keys)