input: Write a function to detect spam emails based on specific keywords like 'viagra', 'cialis', or 'pharmacy'.
  assert is_spam("Get cheap viagra now!") == True
  assert is_spam("Your pharmacy bill is due") == True
  assert is_spam("Hello, how are you?") == False
  assert is_spam("We offer the best cialis deals") == True
output: def is_spam(email_text):
      spam_keywords = ["viagra", "cialis", "pharmacy"]
      email_text_lower = email_text.lower()
      for keyword in spam_keywords:
          if keyword in email_text_lower:
              return True
      return False