Change `getSamples()` return type from `array` to `iterable`

[pounard]

Later in anonymizers, we will have file loaders.

The getSample() method returns an array, but file readers will read files sequentially using generators, which will force us to create a temporary array with all values in memory for nothing.

Using iterable typing and using it accordingly will allow us to never go through an array and gain memory and speed (and avoid potential memory limit errors in constrained environments).