docs: public static synchronized ObjectMapper getLegacyMapperFor(@NonNull Class<?> clazz){
          if(!legacyMappers.containsKey(clazz)){
              ObjectMapper m = new ObjectMapper();
              configureMapper(m);
              m.setAnnotationIntrospector(new IgnoreJsonTypeInfoIntrospector(Collections.<Class>singletonList(clazz)));
              legacyMappers.put(clazz, m);
          }
          return legacyMappers.get(clazz);
      }