How to use the dowhy.causal_estimator.RealizedEstimand function in dowhy

estimator_assumptions = {
            "treatment_effect_homogeneity": (
                "Each unit's treatment {0} is ".format(self._treatment_name) +
                "affected in the same way by common causes of "
                "{0} and {1}".format(self._treatment_name, self._outcome_name)
            ),
            "outcome_effect_homogeneity": (
                "Each unit's outcome {0} is ".format(self._outcome_name) +
                "affected in the same way by common causes of "
                "{0} and {1}".format(self._treatment_name, self._outcome_name)
            ),
        }
        sym_assumptions = {**estimand.estimands["iv"]["assumptions"],
                           **estimator_assumptions}

        symbolic_estimand = RealizedEstimand(estimand,
                                             estimator_name="Wald Estimator")
        symbolic_estimand.update_assumptions(sym_assumptions)
        symbolic_estimand.update_estimand_expression(sym_effect)
        return symbolic_estimand