It seems like the pipeline for "conversational" has been removed, but the suggested code still uses a conversational type of input:

Use a pipeline as a high-level helper

from transformers import pipeline

pipe = pipeline("text2text-generation", model="facebook/blenderbot-400M-distill")
messages = [
{"role": "user", "content": "Who are you?"},
]
pipe(messages)

This code leads to an error.