* if an item is streamable, its value will be retrieved, and a new item containing the value will be returned.
* other, non-streamable items will simply be passed through.
Materialization is helpful if a value is to be processed more than once. It is even mandatory if the a value needs to will be retrieved invalidated before other actions take place that invalidate the resource, such as it is processed (see the deletion of an addressed fileexample below).
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| '''Example'''