anchor.diff:  			 (funcall setter value iter))
   		 row setters)))))))
   
  -(defun (setf tree-model-value) (value model row column)
  +(defgeneric (setf tree-model-value) (value model row column))
  +
  +(defmethod (setf tree-model-value) (value (model tree-model) row column)
     (let ((iter (etypecase row
   		(tree-iter row)
   		(tree-path (multiple-value-bind (valid iter)
  
positive.code:   (call-next-method)
    (%list-store-set-column-types list-store column-types)
    (when column-names
      (setf (object-data list-store 'column-names) column-names))
    (when initial-content
      (loop
       with iter = (make-instance 'tree-iter)
  
negative.code:   (column int)
    (gvalue gvalue))
  
  (defgeneric tree-model-value (model row column))
  
  (defmethod tree-model-value ((model tree-model) row column)
    (let ((index (column-index model column))
  	(iter (etypecase row
  		(tree-iter row)
  