input: Write a function to remove punctuation and whitespace from a string.
  assert remove_punc_and_whitespace("Hello, world!") == "Helloworld"
  assert remove_punc_and_whitespace("Python is great - isn't it?") == "Pythonisgreatisntit"
  assert remove_punc_and_whitespace("No: punctuation... or whitespace!") == "Nopunctuationorwhitespace"
output: def remove_punc_and_whitespace(s):
      import string
      return ''.join(char for char in s if char not in string.punctuation and not char.isspace())