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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 check_token(self, token=None):
 """ ADMIN ONLY. Returns True or False, depending on whether the current token is valid. """

        if token is None:
            token = self.token
        resp, resp_body = self.method_head("tokens/%s" % token, admin=True)
        if resp.status_code in (401, 403):
            raise exc.AuthorizationFailure("You must be an admin to make this "
                    "call.")
        return 200 <= resp.status_code < 300