code: @Override
    public Boolean hexists(final byte[] key, final byte[] field) {
      checkIsInMultiOrPipeline();
      client.hexists(key, field);
      return client.getIntegerReply() == 1;
    }
docs: Test for existence of a specified field in a hash. <b>Time complexity:</b> O(1)
  @param key
  @param field
  @return Return true if the hash stored at key contains the specified field. Return false if the key is
  not found or the field is not present.