def to_chunkstruct(self, chunk_label='CHUNK'):
        """
        Return the chunk structure encoded by this ``ChunkString``.

        :rtype: Tree
        :raise ValueError: If a transformation has generated an
            invalid chunkstring.
        """
        if self._debug < 0: self._verify(self._str, 1)

        # Use this alternating list to create the chunkstruct.
        pieces = []
        index = 0
        piece_in_chunk = 0
        for piece in re.split('[{}]', self._str):

            # Find the list of tokens contained in this piece.
            length = piece.count('<')
            subsequence = self._pieces[index:index+length]

            # Add this list of tokens to our pieces.
            if piece_in_chunk:
                pieces.append(Tree(chunk_label, subsequence))
            else:
                pieces += subsequence

            # Update index, piece_in_chunk
            index += length
            piece_in_chunk = not piece_in_chunk

        return Tree(self._root_label, pieces)
dataset/ETHPy150Open nltk/nltk/nltk/chunk/regexp.py/ChunkString.to_chunkstruct/operator `>` -> `<`