// replace left
if ( leftPrevious == null && leftNext == null ) {
// no other tuples, simply replace
if ( isHandle ) {
fh.removeLeftTuple( peer );
fh.addFirstLeftTuple( newPeer );
} else {
peer.unlinkFromLeftParent();
leftParent.setFirstChild(newPeer);
leftParent.setLastChild(newPeer);