extensions/references-view/src/calls/model.ts/CallsModel/_resolveCalls
class CallsModel:	private async _resolveCalls(call: CallItem): Promise<CallItem[]> {
		if (this.direction === CallsDirection.Incoming) {
			const calls = await vscode.commands.executeCommand<vscode.CallHierarchyIncomingCall[]>('vscode.provideIncomingCalls', call.item);
			return calls ? calls.map(item => new CallItem(this, item.from, call, item.fromRanges.map(range => new vscode.Location(item.from.uri, range)))) : [];
		} else {
			const calls = await vscode.commands.executeCommand<vscode.CallHierarchyOutgoingCall[]>('vscode.provideOutgoingCalls', call.item);
			return calls ? calls.map(item => new CallItem(this, item.to, call, item.fromRanges.map(range => new vscode.Location(call.item.uri, range)))) : [];
		}
	}