docs: def from_uuid(cls, uuid, **extra_data):
          """Load an existing workflow from the database given a UUID.
  
          :param uuid: pass a uuid to an existing workflow.
          :type uuid: str
          """
          model = Workflow.query.get(uuid)
          if model is None:
              raise LookupError(
                  "No workflow with UUID {} was found".format(uuid)
              )
          instance = cls(model=model, **extra_data)
          instance.objects = WorkflowObjectModel.query.filter(
              WorkflowObjectModel.id_workflow == uuid,
              WorkflowObjectModel.id_parent == None,  # noqa
          ).all()
          return instance