'update : If "loc", update *loc* parameter of
legend upon finalizing. If "bbox", update
*bbox_to_anchor* parameter.'

def __init__(self, legend, use_blit=False, update=u'loc'):

    self.legend = legend
    if (update in [u'loc', u'bbox']):
        self._update = update
    else:
        raise ValueError((u"update    parameter    '%s'    is    not    supported." % update))
    DraggableOffsetBox.__init__(self, legend, legend._legend_box, use_blit=use_blit)
