/**
 * Create, cache and return a Node and store it within the owning node. Typical usage:
 *
 *
 * ```
 * listview(people) {
 *     cellFormat {
 *         graphic = cache {
 *             hbox {
 *                 label("Some large Node graph here")
 *             }
 *         }
 *     }
 * }
 * ```
 *
 * Used within a Cell, the cache statement makes sure that the node is only created once per cell during the cell's life time.
 * This greatly reduces memory and performance overhead and should be used in every situation where
 * a node graph is created and assigned to the graphic property of a cell.
 *
 * Note that if you call this function without a a unique key parameter, you will only ever create a single
 * cached node for this parent. The use case for this function is mostly to cache the graphic node of a cell,
 * so for these use cases you don't need to supply a cache key.
 *
 * Remember that you can still update whatever you assign to graphic below it on each `cellFormat` update item callback.
 *
 * Important: Make sure to not cache hard coded data from the current item this cell represents, as this will change
 * when the cell is reused to display another item. Either bind to the itemProperty with select, or use `cellCache` instead.
 */
fun <T : Node> Node.cache(key: Any = "tornadofx.cachedNode", op: EventTarget.() -> T) = properties.getOrPut(key) {
    op(this)
} as T