Method executes mapping between source

        Args:

        -----
            triple_map: SimpleNamespace, Triple Map

def execute(self, triple_map, output, **kwargs):
        """Method executes mapping between source

        Args:

        -----
            triple_map: SimpleNamespace, Triple Map

        """
        subjects = []
        found_elements = self.source.xpath(
            str(triple_map.logicalSource.iterator),
            namespaces=self.xml_ns)
        for element in found_elements:
            subject = self.generate_term(term_map=triple_map.subjectMap,
                                         element=element,
                                         **kwargs)
            start = len(output)
            for row in triple_map.predicateObjectMap:
                predicate = row.predicate
                if row.template is not None:
                    obj_ = self.generate_term(term_map=row, **kwargs)
                    output.add((subject, predicate, obj_))
                if row.parentTriplesMap is not None:
                    self.__handle_parents__(
                        output,
                        parent_map=row.parentTriplesMap,
                        subject=subject,
                        predicate=predicate,
                        **kwargs)
                new_subjects = self.__reference_handler__(
                    output,
                    predicate_obj_map=row,
                    element=element,
                    subject=subject)
                subjects.extend(new_subjects)
                if row.constant is not None:
                    output.add((subject, predicate, row.constant))
            if start < len(output):
                if triple_map.subjectMap.class_ is not None:
                    output.add((subject,
                                NS_MGR.rdf.type.rdflib,
                                triple_map.subjectMap.class_))
                subjects.append(subject)
        return subjects