def get_alphabet_mapping(filename):
    """
    Given a filename, return a 2D list of [alphabet1, alphabet2] representing
    two alphabet list mappings

    """

    with open(filename) as data:
        res = []
        for line in data.read().splitlines():
            alphabet = []
            for letter in line:
                alphabet.append(letter)
            res.append(alphabet)
    return res