<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_mapping(self, points1, points2):
 """ Set to a 3D transformation matrix that maps points1 onto points2. Parameters points1 : array-like, shape (4, 3) Four starting 3D coordinates. points2 : array-like, shape (4, 3) Four ending 3D coordinates. """

        # note: need to transpose because util.functions uses opposite
        # of standard linear algebra order.
        self.matrix = transforms.affine_map(points1, points2).T