Error: "Can't set attribute"

[Norica]

Hello,

I added a setter, but I still get an error. What do I do wrong?
The class is pretty big so I posted just these pieces of code.

@property
    def deadline(self):
        """
        Deadline in milliseconds.
        """
        return self._task_info.deadline
    
    #Added
    @deadline.setter
    def deadline(self, value):
        self._task_info.deadline = value

I want to set the attribute like this:
task.deadline = 22222

And get the error.