<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def rise_per_residue(self):
 """The rise per residue at each point on the Primitive. Notes ----- Each element of the returned list is the rise per residue, at a point on the Primitive. Element i is the distance between primitive[i] and primitive[i + 1]. The final value is None. """

        rprs = [distance(self[i]['CA'], self[i + 1]['CA'])
                for i in range(len(self) - 1)]
        rprs.append(None)
        return rprs