docstr: Releases the resources no longer needed by the metric
  
  This method is called by the RegistrationOptimizer after the required
  iterations have been computed (forward and / or backward) so that the
  SimilarityMetric can safely delete any data it computed as part of the
  initialization
docstr_tok: ["Releases","the","resources","no","longer","needed","by","the","metric","This","method","is","called","by","the","RegistrationOptimizer","after","the","required","iterations","have","been","computed","(","forward","and","\/","or","backward",")","so","that","the","SimilarityMetric","can","safely","delete","any","data","it","computed","as","part","of","the","initialization"]
code: def free_iteration(self):
      r"""Releases the resources no longer needed by the metric
  
      This method is called by the RegistrationOptimizer after the required
      iterations have been computed (forward and / or backward) so that the
      SimilarityMetric can safely delete any data it computed as part of the
      initialization
      """
  
imports: import abc
  import numpy
  from numpy import gradient
  from scipy import ndimage
  from dipy.align import vector_fields
  from dipy.align import sumsqdiff
  from dipy.align import crosscorr
  from dipy.align import expectmax
  from dipy.align import floating
label_desc: Use image node_id 9 for calling the SimilarityMetric obj's underlying member method code with example usage: obj.free_iteration() without return types