lazyFlatMapMutable

Creates and returns new MutableProvider that lazily maps to the value of the MutableProvider returned by transform.

Contrary to flatMapMutable, this does not disable lazy evaluation of this. Consequently, updates (for example in subscribers or observers) are only received after a flat-mapped provider has been resolved by evaluating the returned provider, applying transform.

transform should be a pure function.

The returned provider will only be stored in a WeakReference in the parent providers (this and the result of transform).