serialize method

@override Object serialize()

Serializes the PNF to a transportable format.

Serialization logic:

• If only url and filename exist: returns URL string (toString())
• Otherwise: returns structured Map (toMap())

Implementation

@override
Object serialize() {
  var uri = uriString;
  if (uri.isNotEmpty) {
    return uri;
  }
  // return inner map
  return _wrapper.toMap();
}