UpdateWorkItemTypeDefinition()? how can I use it

I created an VSTS extension with typescript to upload XML code to TFS (WIT code).

UpdateWorkItemTypeDefinition seemed the correct way to do it. But I cannot get it to work. The first param is taking WorkItemTypeTemplateUpdateModel, means .actionType, .template, .templateType and .methodology.

Can please someone explain the usage of these members or (preferred) give a sample please (there is not much documentation on visualstudio.com and I could not find any examples)

.methodology is unclear to me. Is this "agile" vs. "scrum"? Why is this needed at all, if I just want to update the existing WIT? Plus calling the function seems to do nothing, no promise return and no error