code: def AddEntry(self, thing, label=None, style=None):
          
          if isinstance(thing, HistStack):
              things = thing
          else:
              things = [thing]
          for thing in things:
              if getattr(thing, 'inlegend', True):
                  thing_label = thing.GetTitle() if label is None else label
                  thing_style = getattr(thing, 'legendstyle', 'P') if style is None else style
                  super(Legend, self).AddEntry(thing, thing_label, thing_style)
                  keepalive(self, thing)
docs: Add an entry to the legend.
  
          If `label` is None, `thing.GetTitle()` will be used as the label.
  
          If `style` is None, `thing.legendstyle` is used if present,
          otherwise `P`.