def METHOD_NAME(self, iri: str) -> Optional[dm.Difference]:
    query = f"""
        SELECT ?value ?num_val
        WHERE {{
            <{iri}> <{dm.DERIVATION_AGENT_PYTHON_EXAMPLE_HASVALUE}> ?value .
            ?value <{dm.DERIVATION_AGENT_PYTHON_EXAMPLE_NUMVAL}> ?num_val .
        }}"""
    response = self.performQuery(query)
    if len(response) == 1:
        return dm.Difference(
            instance_iri=iri,
            hasValue=dm.Value(instance_iri=response[0]['value'], numVal=response[0]['num_val']),
        )
    else:
        raise Exception(f"There should only be one instance of Value for Difference {iri}, however, found: {response}")