src/vs/workbench/api/common/extHostLanguageFeatures.ts/CallHierarchyAdapter/provideCallsFrom
class CallHierarchyAdapter:	async provideCallsFrom(sessionId: string, itemId: string, token: CancellationToken): Promise<extHostProtocol.IOutgoingCallDto[] | undefined> {
		const item = this._itemFromCache(sessionId, itemId);
		if (!item) {
			throw new Error('missing call hierarchy item');
		}
		const calls = await this._provider.provideCallHierarchyOutgoingCalls(item, token);
		if (!calls) {
			return undefined;
		}
		return calls.map(call => {
			return {
				to: this._cacheAndConvertItem(sessionId, call.to),
				fromRanges: call.fromRanges.map(r => typeConvert.Range.from(r))
			};
		});
	}