docs: <T> Method getPrimaryRangeKeyGetter(Class<T> clazz) {
          synchronized (primaryRangeKeyGetterCache) {
              if ( !primaryRangeKeyGetterCache.containsKey(clazz) ) {
                  Method rangeKeyMethod = null;
                  for ( Method method : getRelevantGetters(clazz) ) {
                      if ( method.getParameterTypes().length == 0
                              && ReflectionUtils.getterOrFieldHasAnnotation(method, DynamoDBRangeKey.class)) {
                          rangeKeyMethod = method;
                          break;
                      }
                  }
                  primaryRangeKeyGetterCache.put(clazz, rangeKeyMethod);
              }
              return primaryRangeKeyGetterCache.get(clazz);
          }
      }