请以python字典形式回答前面的问题，并要求在回答中必须包含'Alice'和'Bob'两个词，且每个词至少出现两次。让这个字典有一个名为"characters"的键，并且字典包含3个这样的键。
user
{
    "characters": ["Alice", "Bob", "Alice"],
    "setting": "unknown",
    "plot": "Alice and Bob had a conversation about Alice's achievements."
}
assistant