fill rectangular area with specified color

def fill_area(self, x, y, width, height, color, opacity = 1):
        """fill rectangular area with specified color"""
        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()