'Return a homomorphism representing the inclusion map of ``self``.
That is, the natural map from ``self`` to ``self.container``.
>>> from sympy.abc import x
>>> from sympy import QQ
>>> QQ.old_poly_ring(x).free_module(2).submodule([x, x]).inclusion_hom()
Matrix([
[1, 0], : <[x, x]> -> QQ[x]**2
[0, 1]])'

def inclusion_hom(self):

    return self.container.identity_hom().restrict_domain(self)
