docs: private static void preload() {
          String preloads = System.getProperty(PRELOAD);
          if (preloads == null) {
              preloads = "java.lang.WeakPairMap,java.lang.WeakPairMap$Pair,java.lang.WeakPairMap$Pair$Weak";
          }
          for (String preload : preloads.split(",")) {
              try {
                  Class.forName(preload, false, null);
              } catch (ClassNotFoundException ignored) {
              }
          }
      }