@classmethod<EOL><INDENT>def _validate(cls, kind):<DEDENT>
if kind not in cls._valid_kinds:<EOL><INDENT>mesg = "<STR_LIT>"<EOL>raise ValueError(mesg.format(*cls._valid_kinds))<EOL><DEDENT>else:<EOL><INDENT>return kind<EOL><DEDENT>
Validate the kind argument.