def METHOD_NAME(self, itemPos, parentPos, offset=(0,0)):
    """
    Anchors the item at its local itemPos to the item's parent at parentPos.
    Both positions are expressed in values relative to the size of the item or parent;
    a value of 0 indicates left or top edge, while 1 indicates right or bottom edge.
    Optionally, offset may be specified to introduce an absolute offset. 
    Example: anchor a box such that its upper-right corner is fixed 10px left
    and 10px down from its parent's upper-right corner::
        box.anchor(itemPos=(1,0), parentPos=(1,0), offset=(-10,10))
    """
    parent = self.parentItem()
    if parent is None:
        raise Exception("Cannot anchor; parent is not set.")
    if self.__parent is not parent:
        if self.__parent is not None:
            self.__parent.geometryChanged.disconnect(self.__geometryChanged)
        self.__parent = parent
        parent.geometryChanged.connect(self.__geometryChanged)
    self.__itemAnchor = itemPos
    self.__parentAnchor = parentPos
    self.__offset = offset
    self.__geometryChanged()