React Native Fetch data from api issue - react-native

Question

I'm trying to fetch data and access it later from an api that involves token authorization. The token will be generating in other places. this is the current fetch method and the error I have. Please help, been stuck here for days.
async getUserToken() {
const userData = await AsyncStorage.getItem("userData")
let data = JSON.parse(userData as string);
let dataString = data._W.token as string
return dataString
}
//fetch file from api here
async componentDidMount(){
try {
const response = await fetch(SOME_RANDOM_API), {
method: 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json',
'Authorization': 'Token' +
await this.getUserToken(),
},
body: JSON.stringify({
document: this.state.document,
name: this.state.name,
size: this.state.size,
file_type: this.state.file_type,
uploaded: this.state.uploaded,
})
})
const responseJson = await response.json();
console.log(responseJson)
// console.log("response is"+ responseJson)
this.setState({
isLoading: false,
dataSource: responseJson,
});
console.log("response 2 is"+ responseJson)
} catch (error) {
console.log("error is"+ error);
}
}
error here
Object {
"detail": "Unsupported media type \"application/json\" in request.",
}
error isTypeError: undefined is not a function (near '...this.state.dataSource.map...')
TypeError: undefined is not a function (near '...this.state.dataSource.map...')