docstr: Return Pearson's X^2 estimate of scale.
docstr_tok: ["Return","Pearson","'s","X^2","estimate","of","scale","."]
code: def estimate_scale(self, Y=None):
      """
      Return Pearson\'s X^2 estimate of scale.
      """
  
      if Y is None:
          Y = self.Y
      resid = Y - self.results.mu
      return (
          np.power(resid, 2) / self.family.variance(self.results.mu)
      ).sum() / self.df_resid
  
imports: import numpy
  from statsmodels.genmod import families
  from statsmodels.sandbox.nonparametric.smoothers import PolySmoother
  from statsmodels.genmod.generalized_linear_model import GLM
  from statsmodels.tools.sm_exceptions import IterationLimitWarning, iteration_limit_doc
  import warnings
label_desc: Use image node_id 3 for calling the Model obj's underlying member method code with example usage: obj.estimate_scale(Y) and returns: unknown