Return True if the APP1 segment at *offset* in *stream* is NOT an
        Exif segment, as determined by the ``'Exif\x00\x00'`` signature at
        offset 2 in the segment.

def _is_non_Exif_APP1_segment(cls, stream, offset):
        """
        Return True if the APP1 segment at *offset* in *stream* is NOT an
        Exif segment, as determined by the ``'Exif\x00\x00'`` signature at
        offset 2 in the segment.
        """
        stream.seek(offset+2)
        exif_signature = stream.read(6)
        return exif_signature != b'Exif\x00\x00'