code: public boolean addTagRemoval(final Tag tag) {
  
          boolean result = false;
          String tagName = tag.getTagName();
          if (CmsStringUtil.isNotEmptyOrWhitespaceOnly(tagName)) {
              result = m_invisibleTags.add(tagName.toLowerCase());
          }
          return result;
      }
docs: Add a tag that will be invisible for {@link NodeVisitor} instances.
  <p>
  
  Not only "this" tag will be invisible but all parsed Tags that have the same name (case
  insensitive).
  <p>
  
  @param tag the tag that will be visible for all {@link NodeVisitor} instances.
  
  @return true if the tag was added to the internal set of tags to remove, false if not (was
  contained before, has no name,...).