class_docstr: collection of descriptive statistical methods for time series
  
      
class_docstr_tok: ["collection","of","descriptive","statistical","methods","for","time","series"]
code: def filter(self, num, den):
      from scipy.signal import lfilter
  
      xfiltered = lfilter(num, den, self.data)
      return self.__class__(
          xfiltered, self.label, self.name + "_filtered"
      )
  
file_path: statsmodels/statsmodels/tsa/descriptivestats.py
imports: import numpy
  from .None import stattools
label_desc: Use image node_id 2 for calling the TsaDescriptive obj's underlying member method code with example usage: obj.filter(num, den) and returns: self