docs: public static <T> StaticValue<T> mutateStaticValue(StaticValue<T> staticValue, Callable<T> initializer) {
          if (multiplex) {
              // Multiplexing case; must check for existing StaticValue
              if (staticValue == null) {
                  // no existing value; create new one with no constructor initializer
                  staticValue = StaticValue.createStaticValue(null);
              }
              // initialize this thread only with the initializer
              staticValue.initialize(getThreadGroup(), initializer);
              return staticValue;
          }
          // Final singleton case; just create a new StaticValue
          return StaticValue.createStaticValue(initializer);
      }