code: def rot(self, t=0., transposed=False):
          
          rotmat = np.array(
              [[np.cos(self._pa+self._omegab*t),np.sin(self._pa+self._omegab*t)],
               [-np.sin(self._pa+self._omegab*t),np.cos(self._pa+self._omegab*t)]])
          if transposed:
              return rotmat.T
          else:
              return rotmat
docs: 2D Rotation matrix for non-zero pa or pattern speed
             to goto the aligned coordinates