code: def load_fixtures(self, nodes=None, progress_callback=None, dry_run=False):
          
  
          if progress_callback and not callable(progress_callback):
              raise Exception('Callback should be callable')
  
          plan = self.get_plan(nodes=nodes)
  
          try:
              with transaction.atomic():
                  self.load_plan(plan=plan, progress_callback=progress_callback)
                  if dry_run:
                      raise DryRun
          except DryRun:
              # Dry-run to get the atomic transaction rolled back
              pass
  
          return len(plan)
docs: Load all fixtures for given nodes.
  
          If no nodes are given all fixtures will be loaded.
          :param list nodes: list of nodes to be loaded.
          :param callable progress_callback: Callback which will be called while
                                             handling the nodes.