<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _gen_s3_path(self, model, props):
 """ Return the part of the S3 path based on inputs The path will be passed to the s3_upload method & will ultimately be merged with the standard AWS S3 URL. An example model type of 'users' with a resource ID of 99 & an API endpoint ending with 'photos' will have a path generated in the following way: users/99/photos/<timestamp>.<extension> The timestamp is a high precision timestamp & the extension is typically 3 characters & derived in the form-data deserializer. """


        now = '%.5f' % time.time()

        return '%s/%s/%s/%s.%s' % (model.rtype, model.rid_value,
                                   self._s3_rtype, now, props['file-ext'])