target-query incorrectly warns on mixed output

[JSCU-CNI]

target-query warns for mixed output when using the users function together with other record yielding function(s). This seems to be caused by the unimplemented users function of the IOSPlugin. This behaviour might also occur when calling other unimplemented functions.

The function find_plugin_functions tries to determine the output type using the attribute __output__ which is not set for this function. In our opinion this warning should not be shown for unimplemented functions which won't even be run when not dealing with - in this example - the IOSPlugin.

We can either add @export(record=EmptyRecord) to these unimplemented functions, or improve the detection logic of find_plugin_functions.