Maya files a suit in Court A for the recovery of a sum of money from her neighbour, Neha. During the proceedings, Neha requests that a third party, Seema, be added to the suit, as Seema is allegedly liable for the debt. Maya objects, claiming that Seema is not a necessary party. Court A then reviews the application and decides that Seema should indeed be included as a defendant.
Which principle of the CPC is applied in this situation?