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

def identity_hom(self):

    return self.base.identity_hom().quotient_codomain(self.killed_module).quotient_domain(self.killed_module)
