Removing members from a Crm user list with user list service's mutateMembers?

Hello,

I'm trying to understand how to add a user list and fill it with members. I've already managed to add members to a list by following the example code.

But, I can't find out how to remove members from the said list. I've tried sending the exact same request using the REMOVE/ SET operators but I received an unknown error (Added below).

The API documents claim that the remove/set operator is supported. Any Idea whats is wrong? 

    response = user_list_service.mutateMembers([mutate_members_operation])

  File "build/bdist.linux-x86_64/egg/googleads/common.py", line 323, in MakeSoapRequest

    for arg in args])

  File "build/bdist.linux-x86_64/egg/googleads/common.py", line 235, in _PackForSuds

    return [_PackForSuds(item, factory) for item in obj]

  File "build/bdist.linux-x86_64/egg/googleads/common.py", line 232, in _PackForSuds

    new_obj[key] = _PackForSuds(obj[key], factory)

  File "build/bdist.linux-x86_64/egg/googleads/common.py", line 232, in _PackForSuds

    new_obj[key] = _PackForSuds(obj[key], factory)

  File "build/bdist.linux-x86_64/egg/googleads/common.py", line 237, in _PackForSuds

    _RecurseOverObject(obj, factory)

  File "build/bdist.linux-x86_64/egg/googleads/common.py", line 255, in _RecurseOverObject

    copy_of_obj = tuple(obj)

TypeError: 'type' object is not iterable

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