def METHOD_NAME(jpeg_instance, mpheader=None):
    """
    Transform the instance of JpegImageFile into
    an instance of MpoImageFile.
    After the call, the JpegImageFile is extended
    to be an MpoImageFile.
    This is essentially useful when opening a JPEG
    file that reveals itself as an MPO, to avoid
    double call to _open.
    """
    jpeg_instance.__class__ = MpoImageFile
    jpeg_instance._after_jpeg_open(mpheader)
    return jpeg_instance