mouse button to shift

{
                        "description": "mouse button to shift",
                        "manipulators": [
                            {
                                "from": {
                                    "modifiers": {
                                        "optional": [
                                            "any"
                                        ]
                                    },
                                    "pointing_button": "button4"
                                },
                                "to": [
                                    {
                                        "key_code": "left_shift"
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    },