code: public Element tagName(String tagName) {
          Validate.notEmpty(tagName, "Tag name must not be empty.");
          tag = Tag.valueOf(tagName, NodeUtils.parser(this).settings()); // maintains the case option of the original parse
          return this;
      }
docs: Change the tag of this element. For example, convert a {@code <span>} to a {@code <div>} with
  {@code el.tagName("div");}.
  
  @param tagName new tag name for this element
  @return this element, for chaining