code: @SuppressWarnings("unchecked")
      public <C extends Client> Optional<C> findClient(final Class<C> clazz) {
          CommonHelper.assertNotNull("clazz", clazz);
          init();
          if (clazz != null) {
              for (final Client client : getClients()) {
                  if (clazz.isAssignableFrom(client.getClass())) {
                      return Optional.of((C) client);
                  }
              }
          }
          LOGGER.debug("No client found for class: {}", clazz);
          return Optional.empty();
      }
docs: Return the right client according to the specific class.
  
  @param clazz class of the client
  @param <C> the kind of client
  @return the right client