input: Write a python function to classify the sentiment of a text using TextBlob.
  assert classify_sentiment('I am a good person')=='positive'
  assert classify_sentiment('I am a bad person')=='negative'
  assert classify_sentiment('I am just a person')=='neutral'
output: from textblob import TextBlob
  
  def classify_sentiment(text):
      analysis = TextBlob(text)
      polarity = analysis.sentiment.polarity
      if polarity > 0:
          return 'positive'
      elif polarity < 0:
          return 'negative'
      else:
          return 'neutral'