input: Write a python function to classify emails as spam or not based on specific keywords.
  assert classify_emails(["buy this now", "hello friend", "save money", "genuine offer"]) == [True, False, True, False]
  assert classify_emails(["limited offer", "buy one get one", "meeting at 5", "save big on sale"]) == [False, True, False, True]
  assert classify_emails(["join us", "exclusive deal now", "quick response", "buy now save later"]) == [False, True, False, True]
output: def classify_emails(emails):
      spam_keywords = {"buy", "save", "offer", "deal"}
      result = []
      for email in emails:
          if any(keyword in email for keyword in spam_keywords):
              result.append(True)
          else:
              result.append(False)
      return result