publicId property
      
      String
      get
      publicId
      
    
    
The read-only publicId property of the DocumentType returns a
formal identifier of the document.
For synthetic DocumentType, this property reflects the value given in
parameter to DOMImplementation.createDocumentType.
For HTML documents, browsers always set it up to html, whatever the
actual DOCTYPE in the source code is. For SVG documents, for example, it
can be "-//W3C//DTD SVG 1.1//EN".
Implementation
external String get publicId;