docstr: Residual degrees of freedom in the fit.
  
  self.N - self.trace()
  
  where self.N is the number of observations of last fit.
docstr_tok: ["Residual","degrees","of","freedom","in","the","fit",".","self.N","-","self.trace","(",")","where","self.N","is","the","number","of","observations","of","last","fit","."]
code: def df_resid(self):
      """
      Residual degrees of freedom in the fit.
  
      self.N - self.trace()
  
      where self.N is the number of observations of last fit.
      """
  
      return self.N - self.trace()
  
imports: import numpy
  import numpy.linalg
  from scipy.linalg import solveh_banded
  from scipy.optimize import golden
  from models import _hbspline
  import warnings
label_desc: Use image node_id 4 for calling the SmoothingSpline obj's underlying member method code with example usage: obj.df_resid() and returns: unknown