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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _words_at_the_beginning(word, tree, prefix=""):
    '''
    We return all portions of the tree corresponding to the beginning
    of `word`. This is used recursively, so we pass the prefix so we
    can return meaningful words+translations.
    '''
    l = []
    if "" in tree:
        l.append([prefix, tree[""]])
    if len(word) > 0 and word[0] in tree:
        l.extend(_words_at_the_beginning(
            word[1:],
            tree[word[0]],
            prefix=prefix+word[0]
        ))
    return l