#includeIn this code example, we create a root node with the value of 1, and then we add two child nodes to it with the values of 2 and 3. We then access the child nodes of the root node and store them in a vector. Finally, we create a new node with the value of 4 and add it as a child to the first child node of the root node. The ModelNode model is a part of the Qt framework, which is a cross-platform application development framework in C++. The Qt framework provides a wide range of libraries and tools for creating scalable and robust applications.int main() { // Creating the root node of the binary tree ModelNode root(1); // Adding child nodes to the root node root.addChild(ModelNode(2)); root.addChild(ModelNode(3)); // Accessing the child nodes of the root node std::vector children = root.getChildren(); // Creating a new node and adding it as a child to one of the existing nodes ModelNode newNode(4); children[0].addChild(newNode); return 0; }