'Adds an item with title ``value`` and point symbol ``point`` to the specified ``category``.'

def add_item(self, category, value, point):

    if (category not in self.items):
        self.items[category] = [OWLegendTitle(category, self)]
    self.items[category].append(OWLegendItem(str(value), point, self))
    self.update_items()
