ISQLQuote vs. str subclass

I have a custom subclass of str called LiteralValue, the purpose of
which is to represent a string which should be passed to Postgres
unmodified. Its getquoted() method simply returns itself. This type
worked as intended with psycopg2 up to version 2.2.x. However, versions
of psycopg2 2.3 and newer no longer call getquoted() on objects of type
LiteralValue. Is this an expected change in behavior?
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Jonathan Ross Rogers