src/vs/workbench/contrib/callHierarchy/browser/callHierarchyPeek.ts/CallHierarchyTreePeekWidget/showModel
class CallHierarchyTreePeekWidget:	async showModel(model: CallHierarchyModel): Promise<void> {

		this._show();
		const viewState = this._treeViewStates.get(this._direction);

		await this._tree.setInput(model, viewState);

		const root = <ITreeNode<callHTree.Call>>this._tree.getNode(model).children[0];
		await this._tree.expand(root.element);

		if (root.children.length === 0) {
			//
			this.showMessage(this._direction === CallHierarchyDirection.CallsFrom
				? localize('empt.callsFrom', "No calls from '{0}'", model.root.name)
				: localize('empt.callsTo', "No callers of '{0}'", model.root.name));

		} else {
			this._parent.dataset['state'] = State.Data;
			if (!viewState || this._tree.getFocus().length === 0) {
				this._tree.setFocus([root.children[0].element]);
			}
			this._tree.domFocus();
			this._updatePreview();
		}
	}