class_docstr: Base class for plotting and computing IRF-related statistics, want to be
  able to handle known and estimated processes
class_docstr_tok: ["Base","class","for","plotting","and","computing","IRF-related","statistics",",","want","to","be","able","to","handle","known","and","estimated","processes"]
code: def cov(self, *args, **kwargs):
      raise NotImplementedError
  
imports: import numpy
  import numpy.linalg
  import scipy.linalg
  from statsmodels.tools.decorators import cache_readonly
  import statsmodels.tsa.tsatools
  import statsmodels.tsa.vector_ar.plotting
  import statsmodels.tsa.vector_ar.util
label_desc: Use image node_id 3 for calling the BaseIRAnalysis obj's underlying member method code with example usage: obj.cov() without return types