OBJ_POINTER - if set, 'arg' is an object pointer, and a hash table
search will be done. If not, a traversal is done.
OBJ_KEY - if set, 'arg', is a hashable item that is not an object.
OBJ_POINTER - if set, 'arg' is an object pointer, and a hash table
search will be done. If not, a traversal is done.
OBJ_KEY - if set, 'arg', is a hashable item that is not an object.