chore: apply pep8-naming rules for naming convention (#8261)

api/core/tools/provider/builtin/qrcode/tools/qrcode_generator.py

@@ -46,7 +46,7 @@ class QRCodeGeneratorTool(BuiltinTool):
             image = self._generate_qrcode(content, border, error_correction)
             image_bytes = self._image_to_byte_array(image)
             return self.create_blob_message(
-                blob=image_bytes, meta={"mime_type": "image/png"}, save_as=self.VARIABLE_KEY.IMAGE.value
+                blob=image_bytes, meta={"mime_type": "image/png"}, save_as=self.VariableKey.IMAGE.value
             )
         except Exception:
             logging.exception(f"Failed to generate QR code for content: {content}")