code: def threshold(self, front_thresh=0.0, rear_thresh=100.0):
          
          data = np.copy(self._data)
          data[data < front_thresh] = 0.0
          data[data > rear_thresh] = 0.0
          return DepthImage(data, self._frame)
docs: Creates a new DepthImage by setting all depths less than
          front_thresh and greater than rear_thresh to 0.
  
          Parameters
          ----------
          front_thresh : float
              The lower-bound threshold.
  
          rear_thresh : float
              The upper bound threshold.
  
          Returns
          -------
          :obj:`DepthImage`
              A new DepthImage created from the thresholding operation.