expects FileInfo

def process_data(self, file_info):
        """expects FileInfo"""
        if self._is_already_processed(file_info):
            self.log.debug("Content file already processed '%s'", str(file_info))
            self.fire(events.FilteredFile(file_info))
            self.fire(events.FileInfoAlreadyProcessed(file_info))
        else:
            return file_info
        return None