input: Write a function to read in a tweet and remove all punctuation, special characters and stopwords. Return the cleaned tweet as a list of words.
  assert clean_tweet("I'm so excited to be going to the #MuseumTour! #BigDay #travel") == ['excited', 'going', 'MuseumTour', 'BigDay', 'travel']
  assert clean_tweet("Wow! This is awesome @username") == ['Wow', 'awesome']
  assert clean_tweet("") == []
  assert clean_tweet("Hello, world!") == ['Hello', 'world']
  assert clean_tweet("My email is john.doe@example.com") == ['My', 'email', 'john', 'doe', 'example', 'com']
output: def clean_tweet(tweet):
      import string
      stopwords = set(["i'm", "to", "be", "going", "the", "is", "this", "my", "at", "is"])
      tweet = tweet.translate(str.maketrans('', '', string.punctuation))
      words = tweet.split()
      cleaned_words = [word for word in words if word.lower() not in stopwords]
      return cleaned_words