def METHOD_NAME(self, pfn, dest, transfer_timeout=None):
    """ Provides access to files stored inside connected the RSE.
        :param pfn: Physical file name of requested file
        :param dest: Name and path of the files when stored at the client
        :param transfer_timeout Transfer timeout (in seconds) - dummy
        :raises DestinationNotAccessible, ServiceUnavailable, SourceNotFound
     """
    if pfn not in self.files:
        raise exception.SourceNotFound(pfn)