columnar::ContainerId::metAssociation Node1 columnar::ContainerId ::metAssociation + idName Node2 columnar::ContainerId ::regularCIBase< xAOD ::MissingETAssociation, xAOD::MissingETAssociationMap > + isContainerId + regularObjectId + regularColumnAccessorArray + isMutable + perEventRange + perEventId Node2->Node1