code: def scroll(self, clicks):
          
          target = self._target
          ratio = 0.90
  
          mult = 1.0
          if clicks > 0:
              mult = ratio**clicks
          elif clicks < 0:
              mult = (1.0 / ratio)**abs(clicks)
  
          z_axis = self._n_pose[:3, 2].flatten()
          eye = self._n_pose[:3, 3].flatten()
          radius = np.linalg.norm(eye - target)
          translation = (mult * radius - radius) * z_axis
          t_tf = np.eye(4)
          t_tf[:3, 3] = translation
          self._n_pose = t_tf.dot(self._n_pose)
  
          z_axis = self._pose[:3, 2].flatten()
          eye = self._pose[:3, 3].flatten()
          radius = np.linalg.norm(eye - target)
          translation = (mult * radius - radius) * z_axis
          t_tf = np.eye(4)
          t_tf[:3, 3] = translation
          self._pose = t_tf.dot(self._pose)
docs: Zoom using a mouse scroll wheel motion.
  
          Parameters
          ----------
          clicks : int
              The number of clicks. Positive numbers indicate forward wheel
              movement.