def METHOD_NAME(self, pos):
    """Return a widget for the line number passed."""
    if pos < 0:
        # line 0 is the start of the file, no more above
        return None, None
    if len(self.lines) > pos:
        # we have that line so return it
        return self.lines[pos], pos
    if self.file is None:
        # file is closed, so there are no more lines
        return None, None
    assert pos == len(self.lines), "out of order request?"
    self.read_next_line()
    return self.lines[-1], pos