code: public Result xml() {
          setContentType(MimeTypes.XML);
          charset = Charsets.UTF_8;
          // If we already have a String content, we must set the type.
          // The renderable object checks whether or not the given String is a valid XML string,
          // or if a transformation is required.
          if (getRenderable() instanceof RenderableString) {
              ((RenderableString) getRenderable()).setType(MimeTypes.XML);
          }
          return this;
      }
docs: Set the content type of this result to {@link MimeTypes#XML}.
  
  @return the same result where you executed this method on. But the content type is now {@link MimeTypes#XML}.