def need_blank(opt, lines):
    """Helper function to get blank line flag.

    Returns True if:

    * ``opt`` is ``True``
    * ``opt`` is ``None`` and ``lines`` has more than one line.

    Args:
        opt: Option.
        lines: Block lines.

    Returns:
        Boolean value.
    """
    return opt is True or (opt is None and len(lines) > 1)