docstr: Nothing to free for the SSD metric
docstr_tok: ["Nothing","to","free","for","the","SSD","metric"]
code: def free_iteration(self):
      r"""
      Nothing to free for the SSD metric
      """
      pass
  
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 SSDMetric obj's underlying member method code with example usage: obj.free_iteration() without return types