Type inference failed. the value of the type parameter t should be mentioned in input types

I am beginner at kotlin and I am trying to filter items which are present in one list, however i am using a loop and iterator for this purpose. I am getting mentioned exception in the if condition `in` here . Can some one guide me where i am wrong.
I am pasting my function here .

fun getGateWays(
gateways: ArrayList<JsonObject>?,
callback: ResponseCallback<ArrayList<JsonObject>, String>
) {


getDistinctGateways(object : ResponseCallback<List<String>?, String>() {

override fun onFailure(failure: String) {
}

override fun onSuccess(response: List<String>?) {

for(e in gateways!!.iterator()){
if(e.get("value") in response){
gateways.remove(e)
}
}
callback.onSuccess(gateways!!)
}

})

}

This is because

gateways.iterator() will give Iterator<JsonObject>
e is of JsonObject type and response is the type List<String>

You have to get a string value of each gateway in the list. You can do it with `asString` method of `JsonObject`:
```
if (e.get("value").asString in response!!) {
gateways.remove(e)
}
```