docstr: This function calculates the intersection between segmentation and
  reference image
  
  :return: intersection map
docstr_tok: ["This","function","calculates","the","intersection","between","segmentation","and","reference","image",":","return",":","intersection","map"]
code: def __intersection_map(self):
      """
      This function calculates the intersection between segmentation and
      reference image
  
      :return: intersection map
      """
      self.check_binary()
      return np.multiply(self.ref, self.seg)
  
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 8 for calling the PairwiseMeasures obj's underlying member method code with example usage: obj.__intersection_map() and returns: np