def split_text(plaintext):
    """Description: takes plaintext and splits them into a list of 2
    characters.

    Arguments:
        plaintext (string): string used to either encode or decode.
    Returns:
        split_text (list): list containing a valid input string in which the
        string is broken into substrings of length 2, with the first break
        point starting at index = 1.
    """
    split_text = []
    count, index = 0, 0
    while count < len(plaintext) // 2:
        split_text.append(plaintext[index] + plaintext[index + 1])
        count += 1
        index += 2
    return split_text