def define(self, names, **kwargs):
        """Define variables within the namespace.

        This is similar to :meth:`.Problem.define` except that names must be
        given as an iterable. This method accepts the same keyword arguments
        as :meth:`.Problem.define`.
        """
        define_kwargs = dict(self._define_kwargs)
        define_kwargs.update(kwargs)
        self._problem.define(
            *((self, name) for name in names), **define_kwargs)