code: public <T,S> T execute(RiakCommand<T,S> command) throws ExecutionException, InterruptedException
      {
          return command.execute(cluster);
      }
docs: Execute a RiakCommand synchronously.
  <p>
  Calling this method causes the client to execute the provided RiakCommand synchronously.
  It will block until the operation completes then either return the response
  on success or throw an exception on failure.
  </p>
  
  @param command
  The RiakCommand to execute.
  @param <T>
  The RiakCommand's return type.
  @param <S> The RiakCommand's query info type.
  @return a response from Riak.
  @throws ExecutionException if the command fails for any reason.
  @throws InterruptedException