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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def tokens(self, tokenset='internal'):
 """ Deserialize and return a YyTokenLattice object for the initial or internal token set, if provided, from the YY format or the JSON-formatted data; otherwise return the original string. Args: tokenset (str):
 return `'initial'` or `'internal'` tokens (default: `'internal'`) Returns: :class:`YyTokenLattice` """

        toks = self.get('tokens', {}).get(tokenset)
        if toks is not None:
            if isinstance(toks, stringtypes):
                toks = YyTokenLattice.from_string(toks)
            elif isinstance(toks, Sequence):
                toks = YyTokenLattice.from_list(toks)
        return toks