code: def fill_area(self, x, y, width, height, color, opacity = 1):
          
          self.save_context()
          self.rectangle(x, y, width, height)
          self._add_instruction("clip")
          self.rectangle(x, y, width, height)
          self.fill(color, opacity)
          self.restore_context()
docs: fill rectangular area with specified color