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.

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)