docs: public <T> FluentValidator on(T t, ValidatorChain chain) {
          Preconditions.checkNotNull(chain, "ValidatorChain should not be NULL");
          final FluentValidator self = this;
          if (CollectionUtil.isEmpty(chain.getValidators())) {
              lastAddCount = 0;
          } else {
              for (Validator v : chain.getValidators()) {
                  composeIfPossible(v, t);
                  doAdd(new ValidatorElement(t, v));
              }
              lastAddCount = chain.getValidators().size();
          }
  
          return this;
      }