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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 token(self):
 """ Returns authorization token provided by Cocaine. The real meaning of the token is determined by its type. For example OAUTH2 token will have "bearer" type. :return: A tuple of token type and body. """

        if self._token is None:
            token_type = os.getenv(TOKEN_TYPE_KEY, '')
            token_body = os.getenv(TOKEN_BODY_KEY, '')
            self._token = _Token(token_type, token_body)
        return self._token