src/vs/workbench/services/workingCopy/common/workingCopyBackupService.ts/WorkingCopyBackupService/backup
class WorkingCopyBackupService:	backup(identifier: IWorkingCopyIdentifier, content?: VSBufferReadableStream | VSBufferReadable, versionId?: number, meta?: IWorkingCopyBackupMeta, token?: CancellationToken): Promise<void> {
		return this.impl.backup(identifier, content, versionId, meta, token);
	}