toMap abstract method

@override MutableMapping toMap()

Converts the PNF to a structured Map (format 3).

Core logic:

• Serializes the data property (TransportableData) into the "data" field of the Map
• Subclasses may override this method to implement lazy serialization for other properties (e.g., defer encoding large file data until this method is called)
• Updates internal state with the serialized data before returning the Map

Returns: Map representation of the PNF (matches JSON structure)

Implementation

@override
MutableMapping toMap();