code: def omitted_parcov(self):
          
          if self.__omitted_parcov is None:
              self.log("loading omitted_parcov")
              self.__load_omitted_parcov()
              self.log("loading omitted_parcov")
          return self.__omitted_parcov
docs: get the omitted prior parameter covariance matrix
  
          Returns
          -------
          omitted_parcov : pyemu.Cov
  
          Note
          ----
          returns a reference
          
          If ErrorVariance.__omitted_parcov is None,
          attribute is dynamically loaded