code: def __load_jco(self):
          
          if self.jco_arg is None:
              return None
              #raise Exception("linear_analysis.__load_jco(): jco_arg is None")
          if isinstance(self.jco_arg, Matrix):
              self.__jco = self.jco_arg
          elif isinstance(self.jco_arg, str):
              self.__jco = self.__fromfile(self.jco_arg,astype=Jco)
          else:
              raise Exception("linear_analysis.__load_jco(): jco_arg must " +
                              "be a matrix object or a file name: " +
                              str(self.jco_arg))
docs: private method to set the jco attribute from a file or a matrix object