code: def gcv(self):
      return (
          self.mse_resid
          / (1.0 - self.hatmatrix_trace() / self.nobs) ** 2
      )
  
imports: from statsmodels.compat.python import lrange
  import numpy
  from statsmodels.tools.decorators import cache_readonly
  from statsmodels.regression.linear_model import OLS, GLS, RegressionResults
  from statsmodels.regression.feasible_gls import atleast_2dcols
label_desc: Use image node_id 4 for calling the TheilRegressionResults obj's underlying member method code with example usage: obj.gcv() and returns: unknown