what is onDelete('cascade') code example

Example 1: on_delete=models.cascade

on_delete=models.CASCADE will delete anything created by the admin if
the admin user is deleted.

Example 2: meaning of on delete cascade

ON DELETE CASCADE clause in MySQL is used to automatically remove the matching records from the child table when we delete the rows from the parent table. If the ON DELETE CASCADE is defined for one FOREIGN KEY clause only, then cascading operations will throw an error.