fun <T, R : Any> Sequence<T>.mapIndexedNotNull(
    transform: (index: Int, T) -> R?
): Sequence<R>

Returns a sequence containing only the non-null results of applying the given transform function to each element and its index in the original sequence.


transform -

function that takes the index of an element and the element itself and returns the result of the transform applied to the element.

The operation is intermediate and stateless.