Help correct the following code, the generate_text function is not defined, 
from transformers import BertForQuestionAnswering, BertTokenizer
import torch

tokenizer = BertTokenizer.from_pretrained('bert-base-uncased')
model = BertForQuestionAnswering.from_pretrained('bert-base-uncased')

output = generate_text("What is the capital of France?")
print(output)
