code: @Override
    public Long del(final byte[]... keys) {
      checkIsInMultiOrPipeline();
      client.del(keys);
      return client.getIntegerReply();
    }
docs: Remove the specified keys. If a given key does not exist no operation is performed for this
  key. The command returns the number of keys removed. Time complexity: O(1)
  @param keys
  @return Integer reply, specifically: an integer greater than 0 if one or more keys were removed
  0 if none of the specified key existed