Azure Python how to link child/related tickets to an already created ticket?

azure-devops/azure/devops/v5_1/work_item_tracking/work_item_tracking_client.py の create_work_item 付近から始め、生成されたシグネチャをリンク先の REST ドキュメントと比較します。既存の work-item relation テストまたはクライアントモデルを確認して、サポートされている方法を判断します。差異またはサポートされているリンクのワークフローが文書化され、適切なテストでカバーされていれば完了です。

I am trying to use the azure-devops python pip package in order to migrate a large amount of Epic/Story/Feature tickets into Azure Devops. I can create singular tickets just fine, but I'm having trouble linking those tickets together by specifying the hierarchy (ticket A is a parent to child tickets B / C / D)

In order to create an EPIC ticket I'm running code like this:

    #set field
    jpo = JsonPatchOperation()
    jpo.from_ = None
    jpo.op = "add"
    jpo.path = "/fields/Microsoft.VSTS.Scheduling.FinishDate"
    jpo.value = default_field
    jpos.append(jpo)
    
    #create work item
    createdWorkItem = wit_client.create_work_item(
        document=jpos,
        project=project.id,
        type="EPIC",
        validate_only=validate_only,
        bypass_rules=bypass_rules,
        suppress_notifications=suppress_notifications
    )

Which works, but now I'm trying to figure out how to give this Epic ticket a linked Child ticket.

In the github repo for this azure-devops python package, I can see that in the definition for create_work_item there is a string variable expand which has an option for Relations

https://github.com/microsoft/azure-devops-python-api/blob/master/azure-devops/azure/devops/v5_1/work_item_tracking/work_item_tracking_client.py#L1578

:param str expand: The expand parameters for work item attributes. Possible options are { None, Relations, Fields, Links, All }.

It's also discussed in the official azure-devops documentation for the create_work_item function:
https://docs.microsoft.com/en-us/rest/api/azure/devops/wit/work-items/create?view=azure-devops-rest-6.0#workitemexpand

But if I add expand='Relations' to my code it results in an error:

    createdWorkItem = wit_client.create_work_item(
        document=jpos,
        project=project.id,
        type="EPIC",
        validate_only=validate_only,
        bypass_rules=bypass_rules,
        suppress_notifications=suppress_notifications,
        expand='Relations'
    )

TypeError: WorkItemTrackingClient.create_work_item() got an unexpected keyword argument 'expand'

Am I using this 'expand' variable correctly? Or is there a different way I should add a child ticket to an epic in azure using python? Thanks