How to use the flyteidl.core.workflow_pb2.WorkflowTemplate function in flyteidl

def demo_task_for_promote(wf_params, a, b, c):
        b.set(a + 1)
        c.set(a + 2)


    @workflow_class()
    class OneTaskWFForPromote(object):
        wf_input = Input(Types.Integer, required=True)
        my_task_node = demo_task_for_promote(a=wf_input)
        wf_output_b = Output(my_task_node.outputs.b, sdk_type=Integer)
        wf_output_c = Output(my_task_node.outputs.c, sdk_type=Integer)


    :rtype: flytekit.models.core.workflow.WorkflowTemplate
    """
    workflow_template_pb = _workflow_pb2.WorkflowTemplate()
    # So that tests that use this work when run from any directory
    basepath = _path.dirname(__file__)
    filepath = _path.abspath(_path.join(basepath, "resources/protos", "OneTaskWFForPromote.pb"))
    with open(filepath, "rb") as fh:
        workflow_template_pb.ParseFromString(fh.read())

    wt = _workflow_model.WorkflowTemplate.from_flyte_idl(workflow_template_pb)
    return wt

def to_flyte_idl(self):
        """
        :rtype: flyteidl.core.workflow_pb2.WorkflowTemplate
        """
        return _core_workflow.WorkflowTemplate(
            id=self.id.to_flyte_idl(),
            metadata=self.metadata.to_flyte_idl(),
            metadata_defaults=self.metadata_defaults.to_flyte_idl(),
            interface=self.interface.to_flyte_idl(),
            nodes=[n.to_flyte_idl() for n in self.nodes],
            outputs=[o.to_flyte_idl() for o in self.outputs],
            failure_node=self.failure_node.to_flyte_idl() if self.failure_node is not None else None
        )