No yes matches during labelling

[nadeemnehru]

While asking for yes/no labels, I labelled 200 pairs and none of them could be labelled yes. After that I stopped and finished labelling. On trying to run
deduper.train(), I got the error
TypeError: descriptor 'union' of 'set' object needs an argument

Is this error because no pair could be labelled yes? Can I get around the situation, when only one of yes/no labels can be assigned for every pair asked?

[fgregg]

This would be an opportunity for a better error message.

[monicatao]

This would be an opportunity for a better error message.

I have an opposite situation where I keep getting yes matches during labeling and seldom get no match. Is it designed to be like this? and why?

Thanks!

[fgregg]

dupe of #565