def METHOD_NAME(self, identifier, extension='.epub', open_access=False, data_source=None, title=None):
    """Returns the path to the hosted EPUB file for the given identifier."""
    bucket = self.get_bucket(
        S3UploaderConfiguration.OA_CONTENT_BUCKET_KEY if open_access
        else S3UploaderConfiguration.PROTECTED_CONTENT_BUCKET_KEY)
    root = self.content_root(bucket)
    METHOD_NAME = root + self.key_join([identifier.identifier])
    return METHOD_NAME