def get_operation_model(svc, fn):
    """Return operation model for method of a service model

    :param svc: AWS service client
    :param fn: method of svc
    :return: operation model for fn
    """
    if isinstance(fn, str):
        func_name = fn
    else:
        func_name = fn.__name__
    return svc._service_model.operation_model(svc._PY_TO_OP_NAME[func_name])