input: Write a python function to remove punctuation and unwanted words from a text string.
  assert clean_text("Hello, world! This is a test.") == "Hello world This is test"
  assert clean_text("A quick brown fox jumps over the lazy dog!") == "quick brown fox jumps over lazy dog"
  assert clean_text("The quick, brown fox; and the lazy dog.") == "quick brown fox lazy dog"
output: def clean_text(text):
      import string
      unwanted_words = {'a', 'an', 'the', 'and', 'or', 'but'}
      translator = str.maketrans('', '', string.punctuation)
      words = text.translate(translator).split()
      cleaned_words = [word for word in words if word.lower() not in unwanted_words]
      return ' '.join(cleaned_words)