src/vs/workbench/contrib/debug/browser/debugSession.ts/DebugSession/getSource
class DebugSession:	getSource(raw?: DebugProtocol.Source): Source {
		let source = new Source(raw, this.getId(), this.uriIdentityService);
		const uriKey = source.uri.toString();
		const found = this.sources.get(uriKey);
		if (found) {
			source = found;
			// merge attributes of new into existing
			source.raw = mixin(source.raw, raw);
			if (source.raw && raw) {
				// Always take the latest presentation hint from adapter #42139
				source.raw.presentationHint = raw.presentationHint;
			}
		} else {
			this.sources.set(uriKey, source);
		}

		return source;
	}