docs: public static void registerLegacyCustomClassesForJSON(List<Pair<String,Class>> classes){
          for(Pair<String,Class> p : classes){
              String s = p.getFirst();
              Class c = p.getRight();
              //Check if it's a valid class to register...
              boolean found = false;
              for( Class<?> c2 : REGISTERABLE_CUSTOM_CLASSES){
                  if(c2.isAssignableFrom(c)){
                      Map<String,String> map = LegacyMappingHelper.legacyMappingForClass(c2);
                      map.put(p.getFirst(), p.getSecond().getName());
                      found = true;
                  }
              }
  
              if(!found){
                  throw new IllegalArgumentException("Cannot register class for legacy JSON deserialization: class " +
                          c.getName() + " is not a subtype of classes " + REGISTERABLE_CUSTOM_CLASSES);
              }
          }
      }