src/vs/workbench/api/common/extHostLanguageFeatures.ts/ExtHostLanguageFeatures/$prepareCallHierarchy
class ExtHostLanguageFeatures:	$prepareCallHierarchy(handle: number, resource: UriComponents, position: IPosition, token: CancellationToken): Promise<extHostProtocol.ICallHierarchyItemDto[] | undefined> {
		return this._withAdapter(handle, CallHierarchyAdapter, adapter => Promise.resolve(adapter.prepareSession(URI.revive(resource), position, token)), undefined, token);
	}