def METHOD_NAME(self, x=None, y=None):
    if x is None or y is None:
        #logging.debug("Must supply both x and y data points, got x:'%s' y:'%s'" % (str(x), str(y)))
        return
    #print('Adding point: %s %s' % (str(x), str(y)))
    if len(self.x_values) == 0:
        #First bar, so start a 0
        self.x_values.append(0)
    else:
        #Second or subsequent bar, so start at last point
        #Which is previous left+width
        items = len(self.x_values)
        last_left = self.x_values[items-1]
        last_width = self.bar_widths[items-1]
        new_left = last_left+last_width
        self.x_values.append(new_left)
    self.bar_widths.append(x)            
    self.y_values.append(y)
    self.bar_bottoms.append(0)