code: def _load_calib(self):
          
          # We'll build the calibration parameters as a dictionary, then
          # convert it to a namedtuple to prevent it from being modified later
          data = {}
  
          # Load the rigid transformation from IMU to velodyne
          data['T_velo_imu'] = self._load_calib_rigid('calib_imu_to_velo.txt')
  
          # Load the camera intrinsics and extrinsics
          data.update(self._load_calib_cam_to_cam(
              'calib_velo_to_cam.txt', 'calib_cam_to_cam.txt'))
  
          # Pre-compute the IMU to rectified camera coordinate transforms
          data['T_cam0_imu'] = data['T_cam0_velo'].dot(data['T_velo_imu'])
          data['T_cam1_imu'] = data['T_cam1_velo'].dot(data['T_velo_imu'])
          data['T_cam2_imu'] = data['T_cam2_velo'].dot(data['T_velo_imu'])
          data['T_cam3_imu'] = data['T_cam3_velo'].dot(data['T_velo_imu'])
  
          self.calib = namedtuple('CalibData', data.keys())(*data.values())
docs: Load and compute intrinsic and extrinsic calibration parameters.