def skip_whitespace(lines):
    i = 0
    while lines[i:] and (not lines[i].strip() or lines[i][0] == ';'):
        i += 1
    return lines[i:]

def next_line(lines):
    lines = skip_whitespace(lines)
    if not lines:
        return [], None
    else:
        line = lines[0].strip()
        return lines[1:], line