code: public IndexRequest textVersion(final Integer textVersion) {
          if (textVersion != null) {
              isTrueArgument("textVersion must be 1, 2 or 3", VALID_TEXT_INDEX_VERSIONS.contains(textVersion));
          }
          this.textVersion = textVersion;
          return this;
      }
docs: Set the text index version number.
  
  @param textVersion the text index version number.
  @return this