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internal val map: MutableMap<Key<*>, Any?> = mutableMapOf()

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    /**
     * Returns an existing ViewModel or creates a new one in the scope (usually, a fragment or
     * an activity), associated with this `ViewModelProvider`.
     *
     *
     * The created ViewModel is associated with the given scope and will be retained
     * as long as the scope is alive (e.g. if it is an activity, until it is
     * finished or process is killed).
     *
     * @param modelClass The class of the ViewModel to create an instance of it if it is not
     * present.
     * @return A ViewModel that is an instance of the given type `T`.
     * @throws IllegalArgumentException if the given [modelClass] is local or anonymous class.
     */
    @MainThread
    public open operator fun <T : ViewModel> get(modelClass: Class<T>): T {
        val canonicalName = modelClass.canonicalName
            ?: throw IllegalArgumentException("Local and anonymous classes can not be ViewModels")
        return get("$DEFAULT_KEY:$canonicalName", modelClass)
    }

    /**
     * Returns an existing ViewModel or creates a new one in the scope (usually, a fragment or
     * an activity), associated with this `ViewModelProvider`.
     *
     * The created ViewModel is associated with the given scope and will be retained
     * as long as the scope is alive (e.g. if it is an activity, until it is
     * finished or process is killed).
     *
     * @param key        The key to use to identify the ViewModel.
     * @param modelClass The class of the ViewModel to create an instance of it if it is not
     * present.
     * @return A ViewModel that is an instance of the given type `T`.
     */
    @Suppress("UNCHECKED_CAST")
    @MainThread
    public open operator fun <T : ViewModel> get(key: String, modelClass: Class<T>): T {
        val viewModel = store[key]
        if (modelClass.isInstance(viewModel)) {
            (factory as? OnRequeryFactory)?.onRequery(viewModel!!)
            return viewModel as T
        } else {
            @Suppress("ControlFlowWithEmptyBody")
            if (viewModel != null) {
                // TODO: log a warning.
            }
        }
        val extras = MutableCreationExtras(defaultCreationExtras)
        extras[VIEW_MODEL_KEY] = key
        // AGP has some desugaring issues associated with compileOnly dependencies so we need to
        // fall back to the other create method to keep from crashing.
        return try {
            factory.create(modelClass, extras)
        } catch (e: AbstractMethodError) {
            factory.create(modelClass)
        }.also { store.put(key, it) }
    }