코틀린 import에러부분을 도저히 모르겠습니다.

Question

package com.rahmat.app.androidchat.feature

import ai.api.AIDataService
import ai.api.model.AIRequest
import ai.api.model.AIResponse
import android.util.Log
import com.google.firebase.database.DatabaseReference
import com.rahmat.app.androidchat.entity.ChatMessage
import org.jetbrains.anko.coroutines.experimental.bg
import org.jetbrains.anko.custom.async

/**
 * Created by muhrahmatullah on 09/10/18.
 */
class MainPresenter(val aiDataAIService: AIDataService,
                    val ref: DatabaseReference) : MainContract.Presenter {

    val aiRequest = AIRequest()

    override fun sendMessage(message: String) {
        val chatMessage = ChatMessage(message, "user")
        ref.child("chat").push().setValue(chatMessage)
        aiRequest.setQuery(message)

        async(UI) {
            val response = bg {
                aiDataAIService.request(aiRequest)
            }
            if (response.await() != null) {
                sendMessageToServer(response.await())
            }else{
                Log.v("test", "didn't send")
            }
        }
    }
    private fun sendMessageToServer(response: AIResponse?) {
        val result = response?.result
        val reply = result?.fulfillment?.speech
        val chatMessage = ChatMessage(reply, "bot")
        ref.child("chat").push().setValue(chatMessage)
    }
}

코드 부분에서 

import kotlinx.coroutines.experimental.android.UI부분이 에러가 뜹니다. alt + enter를 해도 해결되지가 않습니다 에러는 e: java.lang.IllegalStateException: Backend Internal error: Exception during code generation 이라고 뜨네요 검색을 해봐도 도저히 모르겠습니다.