code: def fetch(self):
          
          params = values.of({})
  
          payload = self._version.fetch(
              'GET',
              self._uri,
              params=params,
          )
  
          return InstalledAddOnExtensionInstance(
              self._version,
              payload,
              installed_add_on_sid=self._solution['installed_add_on_sid'],
              sid=self._solution['sid'],
          )
docs: Fetch a InstalledAddOnExtensionInstance
  
          :returns: Fetched InstalledAddOnExtensionInstance
          :rtype: twilio.rest.preview.marketplace.installed_add_on.installed_add_on_extension.InstalledAddOnExtensionInstance