Room Error: Not sure how to handle query method's return type

Error on branch `step13-19_network_and_database`

Seem like occurring after adopt Kotlin 1.6.

https://github.com/googlecodelabs/android-paging/blob/step13-19_network_and_database/build.gradle

```groovy
buildscript {
ext.kotlin_version = '1.6.0'
repositories {
google()
mavenCentral()
}
dependencies {
classpath 'com.android.tools.build:gradle:7.0.4'
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}
}
```

It should be downgrade to kotlin 1.5 or upgrade to Room 2.4 (in alpha)

Start with the build.gradle file in the step13-19_network_and_database branch and inspect the Kotlin and Room versions. Reproduce the query return-type error, then verify the reported version compatibility options; done means the codelab branch builds without the Room error.

Written by the indexing model from the issue text.