code: def run_trial(self, trial_id = 0, until = None, return_env = True, **opts):
          
          # Set-up trial environment and graph
          until=until or self.max_time
          env=self.get_env(trial_id = trial_id, **opts)
          # Set up agents on nodes
          with utils.timer('Simulation {} trial {}'.format(self.name, trial_id)):
              env.run(until)
          if self.dump and not self.dry_run:
              with utils.timer('Dumping simulation {} trial {}'.format(self.name, trial_id)):
                  env.dump(formats = self.dump)
          if return_env:
              return env
docs: Run a single trial of the simulation
  
          Parameters
          ----------
          trial_id : int