def tokens(self):
        """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']
        """
        for content in self.contents:
            if isinstance(content, TokenWithPosition):
                for word in content.split():
                    yield word
            else:
                yield content
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']