def METHOD_NAME(self, proof=True):
    r"""
    Return ``True``, since this in an object of the category
    of integral domains.
    EXAMPLES::
        sage: QQ.is_integral_domain()
        True
        sage: Parent(QQ, category=IntegralDomains()).is_integral_domain()
        True
        sage: L.<z> = LazyLaurentSeriesRing(QQ)                                 # needs sage.combinat
        sage: L.is_integral_domain()                                            # needs sage.combinat
        True
        sage: L.is_integral_domain(proof=True)                                  # needs sage.combinat
        True
    """
    return True