def _intersect_line_line(line1, line2):
    """
    Intersect two straight lines.

    If the lines are parallel, no value is returned.
    :param line1 (Line): Line 1.
    :param line2 (Line): Line 2.
    :return (x, y): Intersection point or nothing.
    """
    denom = line1.a * line2.b - line2.a * line1.b
    if denom == 0:
        return []
    x = (line1.b * line2.c - line2.b * line1.c) / (-denom)
    y = (line1.a * line2.c - line2.a * line1.c) / denom

    return [(x, y)]