Problem 3: Trees (100 + 100 + 200 + 100 + 100 pts)

Recall that the tree abstract data types mentioned in class, can be recursively defined using a root node and (sub)trees.

Tree ADT has one constructor:

• tree(label, branches=[]): Creates a tree with the given label and branches.

We also have the following default selectors in order to get the information for each tree:

• label(tree): returns the tree's label.
• branches(tree): returns the tree's branches.
• is_leaf(object): returns the if a tree is a leaf.