PR #2139 changed this factory so that if given a certain baseType, it will also
recognize any subtype of that type. That is often the right thing to do, but it
is a change in behaviour, and does in fact break at least one current client of
this code. So instead we introduce a new `recognizeSubclasses()` method that
triggers this behaviour. When the method is not called, we revert to the old
behaviour of only recognizing instances of the exact class `baseType`.
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