code: def fix_whitespace(tokens, start, result):
      
      for e in result:
          for child in e.iter():
              child.text = child.text.replace(' , ', ', ')
              for hyphen in HYPHENS:
                  child.text = child.text.replace(' %s ' % hyphen, '%s' % hyphen)
              child.text = re.sub(r'- (.) -', r'-\1-', child.text)
      return result
docs: Fix whitespace around hyphens and commas. Can be used to remove whitespace tokenization artefacts.