code: def tokens(self):
          
          for content in self.contents:
              if isinstance(content, TokenWithPosition):
                  for word in content.split():
                      yield word
              else:
                  yield content
docs: Further breaks down all tokens for a particular expression into
          words and other expressions.
  
          >>> tex = TexEnv('lstlisting', ('var x = 10',))
          >>> list(tex.tokens)
          ['var x = 10']