code: def filled_rectangle(self, x0, y0, x1, y1):
          
          x0, y0, x1, y1 = self.rect_helper(x0, y0, x1, y1)
          for x in range(x0, x1 + 1):
              for y in range(y0, y1 + 1):
                  self.point(x, y, self.color)
docs: Draw a filled rectangle