Load an existing workflow from the database given a UUID.

        :param uuid: pass a uuid to an existing workflow.
        :type uuid: str

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