def flatten_dialogue(dialogue):
    """
    Flatten a dialogue into a single string
    Dialogue are list of turns (list of lists)
    """
    flattened = []
    for turn in dialogue:
        # filter first element of turn if it is none
        if turn[0] != "none":
            flattened.append(" ".join(turn))
        else:
            flattened.append(turn[1])
    return " ".join(flattened)