code: def rotation_matrix(self):
          
          self._normalise()
          product_matrix = np.dot(self._q_matrix(), self._q_bar_matrix().conj().transpose())
          return product_matrix[1:][:,1:]
docs: Get the 3x3 rotation matrix equivalent of the quaternion rotation.
  
          Returns:
              A 3x3 orthogonal rotation matrix as a 3x3 Numpy array
  
          Note:
              This feature only makes sense when referring to a unit quaternion. Calling this method will implicitly normalise the Quaternion object to a unit quaternion if it is not already one.