src/vs/workbench/api/common/extHostDebugService.ts/ExtHostDebugServiceBase/getSession
class ExtHostDebugServiceBase:	private async getSession(dto: IDebugSessionDto): Promise<ExtHostDebugSession> {
		if (dto) {
			if (typeof dto === 'string') {
				const ds = this._debugSessions.get(dto);
				if (ds) {
					return ds;
				}
			} else {
				let ds = this._debugSessions.get(dto.id);
				if (!ds) {
					const folder = await this.getFolder(dto.folderUri);
					const parent = dto.parent ? this._debugSessions.get(dto.parent) : undefined;
					ds = new ExtHostDebugSession(this._debugServiceProxy, dto.id, dto.type, dto.name, folder, dto.configuration, parent);
					this._debugSessions.set(ds.id, ds);
					this._debugServiceProxy.$sessionCached(ds.id);
				}
				return ds;
			}
		}
		throw new Error('cannot find session');
	}