code: def nfev(self):
      return self.res["nfev"]
  
imports: import abc
  import warnings
  import numpy
  import scipy.sparse
  import scipy.optimize
  from scipy.optimize import minimize
  from dipy.utils.optpkg import optional_package
label_desc: Use image node_id 5 for calling the Optimizer obj's underlying member method code with example usage: obj.nfev() and returns: self