code: def get_conditional_instance(self, parameter_names):
          
          if not isinstance(parameter_names, list):
              parameter_names = [parameter_names]
  
          for iname, name in enumerate(parameter_names):
              name = str(name).lower()
              parameter_names[iname] = name
              assert name in self.jco.col_names,\
                  "contribution parameter " + name + " not found jco"
          keep_names = []
          for name in self.jco.col_names:
              if name not in parameter_names:
                  keep_names.append(name)
          if len(keep_names) == 0:
              raise Exception("Schur.contribution_from_Parameters " +
                              "atleast one parameter must remain uncertain")
          #get the reduced predictions
          if self.predictions is None:
              raise Exception("Schur.contribution_from_Parameters " +
                              "no predictions have been set")
          # cond_preds = []
          # for pred in self.predictions:
          #     cond_preds.append(pred.get(keep_names, pred.col_names))
          cond_preds = self.predictions.get(row_names=keep_names)
          la_cond = Schur(jco=self.jco.get(self.jco.row_names, keep_names),
                          parcov=self.parcov.condition_on(parameter_names),
                          obscov=self.obscov, predictions=cond_preds,verbose=False)
          return la_cond
docs: get a new Schur instance that includes conditional update from
          some parameters becoming known perfectly
  
          Parameters
          ----------
          parameter_names : list
              parameters that are to be treated as notionally perfectly
              known
  
          Returns
          -------
          la_cond : Schur
              a new Schur instance conditional on perfect knowledge
              of some parameters
  
          Note
          ----
          this method is used by the get_parameter_contribution() method -
          don't call this method directly