Use DeleteDBSubnetGroup com um AWS SDK

    /**
     * Deletes a subnet group.
     *
     * @param subnetGroupName the identifier of the subnet group to delete
     * @return a {@link CompletableFuture} that completes when the cluster has been deleted
     */
    public CompletableFuture<Void> deleteDBSubnetGroupAsync(String subnetGroupName) {
        DeleteDbSubnetGroupRequest request = DeleteDbSubnetGroupRequest.builder()
                .dbSubnetGroupName(subnetGroupName)
                .build();

        return getAsyncClient().deleteDBSubnetGroup(request)
                .thenAccept(response -> logger.info("🗑️ Deleting Subnet Group: " + subnetGroupName));
    }

def delete_db_subnet_group(neptune_client, subnet_group_name):
    """
    Deletes a Neptune DB subnet group synchronously using Boto3.

    Args:
        neptune_client (boto3.client): The Neptune client.
        subnet_group_name (str): The name of the DB subnet group to delete.

    Raises:
        ClientError: If the delete operation fails.
    """
    delete_group_request = {
        'DBSubnetGroupName': subnet_group_name
    }

    try:
        neptune_client.delete_db_subnet_group(**delete_group_request)
        print(f"️ Deleting Subnet Group: {subnet_group_name}")

    except ClientError as err:
        code = err.response["Error"]["Code"]
        message = err.response["Error"]["Message"]

        if code == "DBSubnetGroupNotFoundFault":
            print(f"Subnet group '{subnet_group_name}' not found or already deleted.")
        elif code == "AccessDeniedException":
            print("Access denied. Please ensure you have the necessary permissions.")
        else:
            print(f"Couldn't delete subnet group. {code}: {message}")
        raise