def seek(self, offset, whence=0):
        """
        seek(offset[, whence]) -> None.  Move to new file position.

        Argument offset is a byte count.  Optional argument whence defaults to
        0 (offset from start of file, offset should be >= 0); other values are 1
        (move relative to current position, positive or negative), and 2 (move
        relative to end of file, usually negative, although many platforms allow
        seeking beyond the end of a file).  If the file is opened in text mode,
        only offsets returned by tell() are legal.  Use of other offsets causes
        undefined behavior.
        Note that not all file objects are seekable.
        """
        assert offset == 0
        self.linepos = 0
        return self.stream.seek(offset, whence)