def METHOD_NAME(self, cls, interface, error_mode):
    """ Checks that a class implements the traits on an interface.
    """
    missing = set(interface.class_traits()).difference(
        set(cls.class_traits())
    )
    if len(missing) > 0:
        return self._handle_error(
            MISSING_TRAIT
            % (
                self._class_name(cls),
                repr(list(missing))[1:-1],
                self._class_name(interface),
            ),
            error_mode,
        )
    return True