'Return the identity homomorphism on ``self``.
>>> from sympy.abc import x
>>> from sympy import QQ
>>> QQ.old_poly_ring(x).free_module(2).submodule([x, x]).identity_hom()
Matrix([
[1, 0], : <[x, x]> -> <[x, x]>
[0, 1]])'

def identity_hom(self):

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