code: def as_dict(self):
          
          return {
              'search_type': self.search_type,
              'agent_id': self.agent_id,
              'id': self.id,
              'price': self.price,
              'price_change': self.price_change,
              'viewings': self.upcoming_viewings,
              'facilities': self.facilities,
              'overviews': self.overviews,
              'formalised_address': self.formalised_address,
              'address_line_1': self.address_line_1,
              'county': self.county,
              'listing_image': self.images,
              'listing_hires_image': self.hires_images,
              'agent': self.agent,
              'agent_url': self.agent_url,
              'contact_number': self.contact_number,
              'daft_link': self.daft_link,
              'shortcode': self.shortcode,
              'date_insert_update': self.date_insert_update,
              'views': self.views,
              'description': self.description,
              'dwelling_type': self.dwelling_type,
              'posted_since': self.posted_since,
              'num_bedrooms': self.bedrooms,
              'num_bathrooms': self.bathrooms,
              'city_center_distance': self.city_center_distance,
              'transport_routes': self.transport_routes,
              'latitude': self.latitude,
              'longitude': self.longitude,
              'ber_code': self.ber_code,
              'commercial_area_size': self.commercial_area_size
          }
docs: Return a Listing object as Dictionary
          :return: dict