docs: public Object getMergePolicy(String className) {
          if (className == null) {
              throw new InvalidConfigurationException("Class name is mandatory!");
          }
          try {
              return policyProvider.getMergePolicy(className);
          } catch (InvalidConfigurationException e) {
              return getOrPutIfAbsent(mergePolicyMap, className, policyConstructorFunction);
          }
      }