code: def get_properties(self, instance, fields):
          
          properties = OrderedDict()
  
          for field in fields:
              if field.write_only:
                  continue
              value = field.get_attribute(instance)
              representation = None
              if value is not None:
                  representation = field.to_representation(value)
              properties[field.field_name] = representation
  
          return properties
docs: Get the feature metadata which will be used for the GeoJSON
          "properties" key.
  
          By default it returns all serializer fields excluding those used for
          the ID, the geometry and the bounding box.
  
          :param instance: The current Django model instance
          :param fields: The list of fields to process (fields already processed have been removed)
          :return: OrderedDict containing the properties of the current feature
          :rtype: OrderedDict