Help with simple nltk Chatbot

[Extra]

I finally figured it out. I had an extra |.
That was driving me mad for so long!

Old (error: |great|):

[
        r"I am fine|i'm (.*) doing good|great|",
        ["Great to hear that, How can I help you?","Nice to hear that",]
    ],

New (Working: |great)

    [
        r"I am fine|i'm (.*) doing good|great",
        ["Great to hear that, How can I help you?","Nice to hear that",]
    ],

I was just messing around with it and noticed that the | was out of place. That happened to be the error but I don't know why.
If anyone knows, could you please explain why that caused that error?
Thanks.