RelationsInspector test backend, with adding and removing GameObjects

TestBackend4.cs

using UnityEngine;
using UnityEditor;
using System.Collections.Generic;
using System.Linq;
using RelationsInspector;
using RelationsInspector.Backend;

public class TestBackend4 : MinimalBackend<GameObject, string>
{
	string searchstring = string.Empty;

	public override IEnumerable<Relation<GameObject, string>> GetRelations( GameObject entity )
	{
		// parent -> entity
		if ( entity.transform.parent != null )
			yield return new Relation<GameObject, string>( entity.transform.parent.gameObject, entity, string.Empty );

		// entity -> children
		foreach ( Transform t in entity.transform )
			yield return new Relation<GameObject, string>( entity, t.gameObject, string.Empty );
	}

	public override void OnEntityContextClick( IEnumerable<GameObject> entities, GenericMenu menu )
	{
		menu.AddItem( new GUIContent( "Add as child" ), false, () => api.InitRelation( entities.ToArray() ) );
		menu.AddItem( new GUIContent( "Delete entity" ), false, () => { foreach ( var e in entities ) DeleteEntity( e ); } );
	}

	void DeleteEntity( GameObject entity )
	{
		api.RemoveEntity( entity );
		Undo.DestroyObjectImmediate( entity );
	}

	public override void CreateRelation( GameObject source, GameObject target)
	{
		Undo.SetTransformParent( target.transform, source.transform, "Adding as child" );
		EditorUtility.SetDirty( source );
		EditorUtility.SetDirty( target );
		api.AddRelation( source, target, string.Empty );
	}

	public override void OnRelationContextClick( Relation<GameObject, string> relation, GenericMenu menu )
	{
		menu.AddItem( new GUIContent( "Un-child" ), false, () => DeleteRelation( relation.Source, relation.Target, relation.Tag ) );
	}

	void DeleteRelation( GameObject source, GameObject target, string tag )
	{
		Undo.SetTransformParent( target.transform, null, "Un-childing" );
		EditorUtility.SetDirty( source );
		EditorUtility.SetDirty( target );
		api.RemoveRelation( source, target, tag );
	}

	public override Rect OnGUI()
	{
		GUILayout.BeginHorizontal( EditorStyles.toolbar );
		{
			if ( GUILayout.Button( "Add GameObject", EditorStyles.toolbarButton, GUILayout.ExpandWidth( false ) ) )
			{
				var newGO = new GameObject();
				Undo.RegisterCreatedObjectUndo( newGO, "Created GameObject" );
				api.AddEntity( newGO, Vector2.zero );
			}
			GUILayout.FlexibleSpace();
			searchstring = BackendUtil.DrawEntitySelectSearchField( searchstring, api );
		}
		GUILayout.EndHorizontal();

		return base.OnGUI();
	}
}