code: public void beginMarkedContent (final COSName tag, final PDPropertyList propertyList) throws IOException
    {
      writeOperand (tag);
      writeOperand (resources.add (propertyList));
      writeOperator ((byte) 'B', (byte) 'D', (byte) 'C');
    }
docs: Begin a marked content sequence with a reference to an entry in the page
  resources' Properties dictionary.
  
  @param tag
  the tag
  @param propertyList
  property list
  @throws IOException
  If the content stream could not be written