Write a Python function find_key() that takes two arguments, a dictionary and a possible value in that dictionary. It returns the key for that value in the dictionary if the value indeed occurs in the dictionary; otherwise, it returns None. If the value occurs several times in the dictionary, any associated key will do. (My solution has 3 or 4 lines.) The following is test code, followed by the output. if __name__ == '__main__': d = {'a': 1, 'b': 5, 'c': 3, 'd': 4} print(find_key(d, 3)) print(find_key(d, 2)) Output c None