def doc_summary(lines):
    """Extract summary of docs."""
    summary = []
    for line in lines:
        stripped = line.strip().lower()
        if (stripped.startswith('to use this normalizer') or
                stripped.startswith('use ``method')):
            continue
        if (line.startswith('Parameters') or line.startswith('Example')
                or line.startswith('.. note::')):
            break
        summary.append(line)
    return summary