MyDataSource.kt

<!-- Copyright 2020 Google LLC.	
   SPDX-License-Identifier: Apache-2.0 -->

fun flowFrom(api: CallbackBasedApi): Flow<T> = callbackFlow {
    val callback = object : Callback {
        override fun onNextValue(value: T) {
            offer(value)
        }
        override fun onApiError(cause: Throwable) {
            close(cause)
        }
        override fun onCompleted() = close()
    }

    api.register(callback)
    awaitClose { api.unregister(callback) }
}