addLeftItem method
Add Left Item
Implementation
@override
void addLeftItem(IMindMapNode item) {
_leftItems.add(item);
item.setParentNode(this);
item.setNodeType(NodeType.left);
refresh();
///if (getNodeType() == NodeType.root && _leftItems.length == 1) {
getMindMap()?.refresh();
///}
/// getMindMap()?.refresh();
getMindMap()?.onChanged();
}