Problem 3.1 : Nut Finder (100 pts)

The squirrels on campus need your help! There are a lot of trees on campus and the squirrels would like to know which ones contain nuts. Define the function nut_finder, which takes in a tree and returns True if the tree contains a node with the value 'nut' and False otherwise.

def nut_finder(t):
    """Returns True if t contains a node with the value 'nut' and
    False otherwise.

    >>> scrat = tree('nut')
    >>> nut_finder(scrat)
    True
    >>> sproul = tree('roots', [tree('branch1', [tree('leaf'), tree('nut')]), tree('branch2')])
    >>> nut_finder(sproul)
    True
    >>> numbers = tree(1, [tree(2), tree(3, [tree(4), tree(5)]), tree(6, [tree(7)])])
    >>> nut_finder(numbers)
    False
    >>> t = tree(1, [tree('nut',[tree('not nut')])])
    >>> nut_finder(t)
    True
    """
    "*** YOUR CODE HERE ***"