Return a variable set of the given names in the namespace.

        >>> v = prob.namespace(name='v')
        >>> v.define([1, 2, 5], lower=0, upper=10)
        >>> prob.add_linear_constraints(v.set([1, 2]) >= 4)

def set(self, names):
        """Return a variable set of the given names in the namespace.

        >>> v = prob.namespace(name='v')
        >>> v.define([1, 2, 5], lower=0, upper=10)
        >>> prob.add_linear_constraints(v.set([1, 2]) >= 4)
        """
        return self._problem.set((self, name) for name in names)