docs: public <K> JoinOperatorSetsPredicateBase where(KeySelector<I1, K> keySelector) {
  		TypeInformation<K> keyType = TypeExtractor.getKeySelectorTypes(keySelector, input1.getType());
  		return new JoinOperatorSetsPredicateBase(new Keys.SelectorFunctionKeys<>(keySelector, input1.getType(), keyType));
  	}