def merge_lines(lines):
    """Merge every line that begins with whitespace with its predecessor.  May
    raise a ParseError."""
    new_lines = []
    offset = 0
    for offset, line in enumerate(lines):
        if len(line) > 0 and not line.isspace():
            break
    lines = lines[offset:]
    if starts_with_whitespace(lines[0]):
        raise ParseError("%d: '%s': Keys cannot be indented.")
    for line in lines:
        if starts_with_whitespace(line):
            new_lines[-1] += line
        else:
            new_lines.append(line)
    return [line.strip() for line in new_lines]
Merge every line that begins with whitespace with its predecessor.  May
    raise a ParseError.
recipes/Python/576996_RFC_822style_parser/recipe-576996.py