def change_first_point_by_index(self, point_idx):
ia.do_assert(<NUM_LIT:0> <= point_idx < len(self.exterior))<EOL>if point_idx == <NUM_LIT:0>:<EOL><INDENT>return self.deepcopy()<EOL><DEDENT>exterior = np.concatenate(<EOL>(self.exterior[point_idx:, :], self.exterior[:point_idx, :]),<EOL>axis=<NUM_LIT:0><EOL>)<EOL>return self.deepcopy(exterior=exterior)<EOL>
Set the first point of the exterior to the given point based on its index.

Note: This method does *not* work in-place.

Parameters
----------
point_idx : int
    Index of the desired starting point.

Returns
-------
imgaug.Polygon
    Copy of this polygon with the new point order.