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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def triangle(self, x1, y1, x2, y2, x3, y3, color="black", outline=False, outline_color="black"):
 """ Draws a triangle between 3 points :param int x1: The x position of the starting point. :param int y1: The y position of the starting point. :param int x2: The x position of the middle point. :param int y2: The y position of the middle point. :param int x3: The x position of the end point. :param int y3: The y position of the end point. :param str color: The color of the shape. Defaults to `"black"`. :param int outline: `0` or `False` is no outline. `True` or value > 1 sets an outline. Defaults to `False`. :param str outline_color: The color of the outline. Defaults to `"black"`. :return: The id of the shape. """

        return self.polygon(
            x1, y1, x2, y2, x3, y3, 
            color=color, 
            outline=outline, 
            outline_color=outline_color)