def _check_signature(self, oauth_request, consumer, token):
        timestamp, nonce = oauth_request._get_timestamp_nonce()
        self._check_timestamp(timestamp)
        self._check_nonce(consumer, token, nonce)
        signature_method = self._get_signature_method(oauth_request)
        try:
            signature = oauth_request.get_parameter('oauth_signature')
        except:
            raise OAuthError('Missing signature.')
        # validate the signature
        valid_sig = signature_method.check_signature(oauth_request, consumer, token, signature)
        if not valid_sig:
            key, base = signature_method.build_signature_base_string(oauth_request, consumer, token)
            raise OAuthError(base % 'Invalid signature. Expected signature base string: %s')
        built = signature_method.build_signature(oauth_request, consumer, token)
dataset/ETHPy150Open benadida/helios-server/helios_auth/security/oauth.py/OAuthServer._check_signature/swapped operands of `%`