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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_relationship(self, session, query, api_type, obj_id, rel_key):
 """ Fetch a collection of related resource types and ids. :param session: SQLAlchemy session :param query: Dict of query args :param api_type: Type of the resource :param obj_id: ID of the resource :param rel_key: Key of the relationship to fetch """

        resource = self._fetch_resource(session, api_type, obj_id,
                                        Permissions.VIEW)
        if rel_key not in resource.__jsonapi_map_to_py__.keys():
            raise RelationshipNotFoundError(resource, resource, rel_key)
        py_key = resource.__jsonapi_map_to_py__[rel_key]
        relationship = self._get_relationship(resource, py_key,
                                              Permissions.VIEW)
        response = JSONAPIResponse()

        related = get_rel_desc(resource, relationship.key,
                               RelationshipActions.GET)(resource)

        if relationship.direction == MANYTOONE:
            if related is None:
                response.data['data'] = None
            else:
                try:
                    response.data['data'] = self._render_short_instance(
                        related)
                except PermissionDeniedError:
                    response.data['data'] = None
        else:
            response.data['data'] = []
            for item in related:
                try:
                    response.data['data'].append(
                        self._render_short_instance(item))
                except PermissionDeniedError:
                    continue

        return response