Method _registerNode

src/cdk/tree/tree.ts:823–826

* Adds the specified node component to the tree's internal registry. * * This primarily facilitates keyboard navigation.

(node: CdkTreeNode<T, K>)

   * This primarily facilitates keyboard navigation.
   */
  _registerNode(node: CdkTreeNode<T, K>) {
    this._nodes.value.set(this._getExpansionKey(node.data), node);
    this._nodes.next(this._nodes.value);
  }

  /** Removes the specified node component from the tree's internal registry. */
  _unregisterNode(node: CdkTreeNode<T, K>) {