def parse_title(line):
    """if this is title, return Tuple[level, content],

    @type line: str
    @return: Optional[Tuple[level, content]]
    """
    line = line.strip()
    if not line.startswith('#'):
        return None
    sharp_count = 0
    for c in line:
        if c == '#':
            sharp_count += 1
        else:
            break
    if sharp_count == len(line):
        return None
    title = line[sharp_count:].strip()
    return sharp_count, title