code: def collapse_whitespace(text):
      
      if text is None:
          return None
      if hasattr(text, 'xpath'):
          text = text.xpath('string()')
      text = re.sub('\s+', ' ', text)
      return text.strip()
docs: Collapse all consecutive whitespace, newlines and tabs
      in a string into single whitespaces, and strip the outer
      whitespace. This will also accept an ``lxml`` element and
      extract all text.