This read only variable returns the index of the object
that the instance has been created from. This is not the
same as the object name, which is a string and can be found using
as this function returns the index number, which is a unique number
that GameMaker: Studio assigns to every object at the time
obj_name = object_get_name(object_index);
The above code will use the object_index to find the name of the object that the current instance has been created from.