code: def __init__(self, reg_img, ref_img, measures=None):
      self.reg = reg_img
      self.ref = ref_img
      self.measures = measures
  
      self.m_dict = {
          "mse": (self.mse, "MSE"),
          "rmse": (self.rmse, "RMSE"),
          "mae": (self.mae, "MAE"),
          "r2": (self.r2, "R2"),
      }
  
imports: from __future__ import absolute_import, print_function
  import numpy
  from scipy import ndimage
  from niftynet.utilities.util_common import MorphologyOps, CacheFunctionOutput
label_desc: Use image node_id 1 to create a new PairwiseMeasuresRegression object from inherited base classes: object with example: obj = PairwiseMeasuresRegression(reg_img, ref_img, measures)