In this question you will use dictionaries to implement a simple version of a data structure often

used for storing large dictionaries of words efficiently, namely a trie or a prefix tree. The way a

trie works, is that each level stores one letter of a word, and then links to another level. This

combines words with like prefixes, which makes searching and storing the information much

easier:

For the purposes of this assignment, we will consider each level of the structure a dictionary with

keys that are the next letter in the word, and values that are dictionaries of the next level. In order

to know when we have reached a word, we will add a key, 'word', with boolean value True, at

any layer where the path there represents a full word.