'Multiply ``self`` by the ideal ``I``.
>>> from sympy.abc import x
>>> from sympy import QQ
>>> I = QQ.old_poly_ring(x).ideal(x**2)
>>> M = QQ.old_poly_ring(x).free_module(2).submodule([1, 1])
>>> I*M
<[x**2, x**2]>'

def multiply_ideal(self, I):

    return self.submodule(*[(x * g) for [x] in I._module.gens for g in self.gens])
