input: Write a function to classify the sentiment of movie reviews using Natural Language Processing. The function should take a string representing a movie review as input and return 'positive' or 'negative' based on the sentiment analysis. If the negative sentiment score is higher, return 'negative', otherwise return 'positive'.
  
  assert classify_sentiment("The movie was terrible. It felt like it would never end!")=='negative'
  assert classify_sentiment("The movie was amazing and full of surprises!")=='positive'
  assert classify_sentiment("Neither good nor bad. Just average.")=='positive'
  assert classify_sentiment("This film was a complete disappointment.")=='negative'
  assert classify_sentiment("")=='positive'
output: def classify_sentiment(review):
      from textblob import TextBlob
      blob = TextBlob(review)
      sentiment_score = blob.sentiment.polarity
      if sentiment_score < 0:
          return 'negative'
      else:
          return 'positive'