from typing import List


def comment_lines(lines: List[str]) -> List[str]:
    """
    Adds a multi line comment to a List of source lines.

    :param lines: The source lines to be commented.
    :returns: The commented List of of source lines.
    """

    lines[0] = f'"""{lines[0]}'
    if not lines[-1].endswith("\n"):
        lines[-1] += "\n"
    lines[-1] = f'{lines[-1]}"""'
    return lines