def METHOD_NAME(self):
    r"""
    Return the ring of which this is the ideal monoid.
    EXAMPLES::
        sage: R = QuadraticField(-23, 'a')                                          # needs sage.rings.number_field
        sage: from sage.rings.ideal_monoid import IdealMonoid
        sage: M = IdealMonoid(R); M.ring() is R                                     # needs sage.rings.number_field
        True
    """
    return self.__R