Return a |Tiff| instance parsed from the Exif APP1 segment of
        *segment_length* at *offset* in *stream*.

def _tiff_from_exif_segment(cls, stream, offset, segment_length):
        """
        Return a |Tiff| instance parsed from the Exif APP1 segment of
        *segment_length* at *offset* in *stream*.
        """
        # wrap full segment in its own stream and feed to Tiff()
        stream.seek(offset+8)
        segment_bytes = stream.read(segment_length-8)
        substream = BytesIO(segment_bytes)
        return Tiff.from_stream(substream)