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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 decode_token(self, token):
 """Decode Authorization token, return None if token invalid"""

        key = current_app.secret_key
        if key is None:
            if current_app.debug:
                current_app.logger.debug("app.secret_key not set")
            return None
        try:
            return jwt.decode(
                token, key,
                algorithms=[self.config["algorithm"]],
                options={'require_exp': True}
            )
        except jwt.InvalidTokenError:
            return None