def METHOD_NAME(region, partition):
    """
    Returns True if the provided region and partition are a valid pair.
    """
    valid_matches = [
        ("cn-", "aws-cn"),
        ("us-gov-", "aws-us-gov"),
        ("us-gov-iso-", "aws-iso"),
        ("us-gov-iso-b-", "aws-iso-b"),
    ]
    for prefix, expected_partition in valid_matches:
        if region.startswith(prefix):
            return partition == expected_partition
    return partition == "aws"