valid_object - allows control over which objects can be loaded

int valid_object( object obj );

After loading an object, the driver will call valid_object() with the newly
created object as its argument, in the master object.  If the function
exists, and returns 0, then the object will be destructed and the efun that
caused it to load will error out.  If it does not exist, or returns 1, then
loading will proceed as normal.  This is called before the object has a
chance to execute any code, including create(), so not much should be
assumed about the object except that file_name(obj) is valid.

See also:
 valid_override