code: def _get_model_without_dependencies(self, models_dict):
          '''
          Helper function to find the next model that should be created
          '''
          next_model = None
          if not models_dict:
              return next_model
  
          for model, dependencies in six.iteritems(models_dict):
              if dependencies == []:
                  next_model = model
                  break
  
          if next_model is None:
              raise ValueError('incomplete model definitions, models in dependency '
                               'list not defined: {0}'.format(models_dict))
  
          # remove the model from other depednencies before returning
          models_dict.pop(next_model)
          for model, dep_list in six.iteritems(models_dict):
              if next_model in dep_list:
                  dep_list.remove(next_model)
  
          return next_modef _get_model_without_dependencies(self, models_dict):
          '''
          Helper function to find the next model that should be created
          '''
          next_model = None
          if not models_dict:
              return next_model
  
          for model, dependencies in six.iteritems(models_dict):
              if dependencies == []:
                  next_model = model
                  break
  
          if next_model is None:
              raise ValueError('incomplete model definitions, models in dependency '
                               'list not defined: {0}'.format(models_dict))
  
          # remove the model from other depednencies before returning
          models_dict.pop(next_model)
          for model, dep_list in six.iteritems(models_dict):
              if next_model in dep_list:
                  dep_list.remove(next_model)
  
          return next_model
docs: Helper function to find the next model that should be created