Fix that toHierarchy couldn't be found. Updated docs and test.

types/TreeView/TreeView.svelte.d.ts

@@ -20,12 +20,6 @@ type $Props = {
    */
   nodes?: Array<TreeNode>;
 
-  /**
-   * Provide a flat array of nodes to render
-   * @default []
-   */
-  nodesFlat?: Array<TreeNode & { pid?: any }>;
-
   /**
    * Set the current active node id
    * Only one node can be active
@@ -100,6 +94,11 @@ export default class TreeView extends SvelteComponentTyped<
    */
   collapseAll: () => void;
 
+  /**
+   * Create a nested array from a flat array
+   */
+  toHierarchy: (flatArray: TreeNode[] & { pid?: any }[]) => TreeNode[];
+
   /**
    * Programmatically expand a subset of nodes.
    * Expands all nodes if no argument is provided