input: Write a python function to convert a sentence to Pig Latin.
  assert pig_latin_sentence("I went to the store.") == "Iway entway otay ethay orestay."
  assert pig_latin_sentence("Hello world") == "Ellohay orldway"
  assert pig_latin_sentence("Python is fun") == "ythonPay isway unfay"
output: def pig_latin_sentence(sentence):
      def pig_latin_word(word):
          if word[0] in 'aeiouAEIOU':
              return word + 'way'
          else:
              return word[1:] + word[0] + 'ay'
      
      words = sentence.split()
      pig_latin_words = [pig_latin_word(word) if word.isalpha() else word[:-1] + pig_latin_word(word[:-1])[-2:] + word[-1] for word in words]
      return ' '.join(pig_latin_words)