docs: private JointParsingState.Action getAction(int l, int r, Target targets) {
  		if (targets.getHead(l) == r && modifierNumOf(l, targets) == 0)
  			return JointParsingState.Action.RIGHT;
  		if (targets.getHead(r) == l && modifierNumOf(r, targets) == 0)
  			return JointParsingState.Action.LEFT;
  		return JointParsingState.Action.SHIFT;
  	}