code: public synchronized void close() throws IOException {
  		// reject modification of already closed node
  		if(isOpen==false) {
  			throw new IOException("Attempted to close already closed tag '" + name + "'!");
  		}
  		// close previously opened child node, if present
  		if(lastChildNode!=null) {
  			// close regular child node
  			lastChildNode.close();
  			// on regular nodes and comments, write closing tag into new line
  			if((lastChildNode instanceof SXTextNode)==false) {
  				writer.write("\n");
  				indentLine();
  			}
  			// write closing text
  			writer.write("</" + name + ">");
  			lastChildNode = null;
  		} else {
  			// no siblings, close unique tag
  			writer.write("/>");
  		}
  		isOpen = false;
  	}
docs: Closes and finalizes this node.
  <b>WARNING:</b> Tags <b>must not be closed manually</b>, but by closing
  their enclosing document.