// Necessary for EdgeConnector, which creates temporary edges
public Edge()
{
layer = -1;
styleSheets.Add(AssetDatabase.LoadAssetAtPath <StyleSheet>(UICreationHelper.templatePath + "Edge.uss"));
RegisterCallback <AttachToPanelEvent>(OnTargetAttachedToPanel);
RegisterCallback <DetachFromPanelEvent>(OnTargetDetachedFromPanel);
m_EdgeBubble = new EdgeBubble();
}