code: def default(self, obj):
          
          if obj is None:
              return []
          elif isinstance(obj, list):
              return [i.as_dictionary() for i in obj]
          elif isinstance(obj, dict):
              return self._keys_to_camel_case(obj)
          else:
              return obj.as_dictionary()
docs: Convert an object to a form ready to dump to json.
  
          :param obj: Object being serialized. The type of this object must be one of the following: None; a single object derived from the Pio class; or a list of objects, each derived from the Pio class.
          :return: List of dictionaries, each representing a physical information object, ready to be serialized.