input: Write a python function to classify emails based on their content and return the type of email.
  assert email_classification('ShippingConfirmation@example.com') == 'Shipping Confirmation'
  assert email_classification('Subscriber@example.com') == 'Subscriber'
  assert email_classification('CommentResponse@example.com') == 'Comment Response'
  assert email_classification('UnknownEmail@example.com') == 'Unknown'
output: def email_classification(email):
      if 'ShippingConfirmation' in email:
          return 'Shipping Confirmation'
      elif 'Subscriber' in email:
          return 'Subscriber'
      elif 'CommentResponse' in email:
          return 'Comment Response'
      else:
          return 'Unknown'