Return true if the file already has a manifest file in the backend.
        
        :param fpath: potential path to the manifest file
        :returns: bool

def already_converted(self, fpath):
        """Return true if the file already has a manifest file in the backend.
        
        :param fpath: potential path to the manifest file
        :returns: bool
        """
        manifest_fpath = os.path.join(self.backend.directory,
                                      os.path.basename(fpath),
                                      'manifest.json')
        return os.path.isfile(manifest_fpath)