def _remove_checksum(lines):
    """Remove metadata comments giving a checksum.

    Adblock Plus is no longer verifying checksums, so we don't have to
    calculate the checksum for the resulting filter list. But we have
    to strip them for compatibility with older versions of Adblock Plus
    and other ad blockers which might still verify a checksum if given.
    """
    for line in lines:
        if line.type != 'metadata' or line.key.lower() != 'checksum':
            yield line
