def __message_completion(ctext):
    """
        Input: ctext - List of lists (4x4 matrix)

        Output: result_string - String (Obviously)

        This method fuses the matrix back to string. Takes each byte (1 element of matrix)
        and converts it to letter, which it concatenates to the result string.
    """
    result_string = ''
    for i in range(4):
        for j in range(4):
            letter = chr(ctext[i][j])
            result_string += letter
    return result_string
