is fairly opaque; therefore as our first example, we demonstrate in Listing 2 the optimization of JK (Coulomb and exchange) fitting sets for the first three noble gases, for the cc-pVnZ orbital basis sets, n = T, Q, 5. For these calculations we used the ORCA (version 5.0.3) backend, an even-tempered guess, and the default preconditioner, which simply enforces that the exponents remain positive.