Complete the implementation of the spanTree() method. To test your program run t

Complete the implementation of the spanTree() method.
To test your program run the run() method in the GraphDemoView class of the view.py file.
Your program’s output should look like the following:
Main menu
1 Input a graph from the keyboard
2 Input a graph from a file
3 View the current graph
4 Single source shortest paths
5 Minimum spanning tree
6 Topological sort
7 Exit the program
Enter a number [1-7]: 2
Enter the file name: topo.txt
Graph created successfully
Main menu
1 Input a graph from the keyboard
2 Input a graph from a file
3 View the current graph
4 Single source shortest paths
5 Minimum spanning tree
6 Topological sort
7 Exit the program
Enter a number [1-7]: 5
Tree: p>s:0 p>q:0 s>t:0 q>r:0
Main menu
1 Input a graph from the keyboard
2 Input a graph from a file
3 View the current graph
4 Single source shortest paths
5 Minimum spanning tree
6 Topological sort
7 Exit the program
Enter a number [1-7]: 7