Override Backend.convert() to add fast paths for BVVs and BoolVs.

def convert(self, expr):
        """
        Override Backend.convert() to add fast paths for BVVs and BoolVs.
        """
        if type(expr) is BV:
            if expr.op == "BVV":
                cached_obj = self._object_cache.get(expr._cache_key, None)
                if cached_obj is None:
                    cached_obj = self.BVV(*expr.args)
                    self._object_cache[expr._cache_key] = cached_obj
                return cached_obj
        if type(expr) is Bool and expr.op == "BoolV":
            return expr.args[0]
        return super().convert(expr)