Is it possible to explicitly describe the gauge transformation $F$ that appears in Theorem XIX.4.3 of Kassel's [Quantum groups](https://doi.org/10.1007/978-1-4612-0783-2), such that  such that $U_{\hbar}(\mathfrak{g})$ and $(U(\mathfrak{g})[[\hbar]])_F$ are isomorphic?