I am trying to get a model based on the Brand. But getting the error when selection the next option

Error says bikeBrand is not a Function

Below is the Json data getting from backend

response from backend { BMW:["F900R", "F900XR"], KTM:["125 Duke", "250 Duke"]}

Then storing on the state using useState hook in React

const [bikeBrands, setBikeBrands] = useState("")

First option value is storing in below hook too

const [selectedBrand, setSelectedBrand] = useState("")

Problem is in the second selection option.

<select onChange={(e) => setSelectedBrand(e.target.value)}>
                        <option>Choose brand</option>
                        {Object.keys(bikeBrands).map((bikeBrand, index) => {
                            return <option>{bikeBrand}</option>
                        })}
                    </select>
                    <select onChange={(e) => setModel(e.target.value)}>
                        <option>Choose Model</option>
                        {Object.keys(bikeBrands).map((bikeBrand, index) => {
                            bikeBrand.map((brandModels, index) => {
                                return <option>{brandModels}</option>
                            })
                        })}

                    </select>