input: Write a python function to ensure a given text starts with an uppercase letter, ends with a period, and has proper punctuation.
  assert punctuate('this is a string of text')=='This is a string of text.'
  assert punctuate('hello world')=='Hello world.'
  assert punctuate('Python programming?')=='Python programming. '
  assert punctuate('example, text')=='Example, text. '
output: def punctuate(text):
      text = text.strip()
      if not text.endswith('.'):
          text = text.rstrip('?.!') + '.'
      text = text[0].upper() + text[1:]
      return text