how do I filter the vector to construct a list

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I am writing a history clipboard, and I want to switch the content type, for example, I want to press the **All** button to show all content, press **Text** to only show the text contents, or press **Image** to only show image contents

I have a field `contents: Vector` and the Content is

```rust
enum Content {
Text(...),
Image(...)
}
```

I pass `AppData::contents` to the `List::lens` to show all contents, but how do I filter the vector, when I just want to show text or image

Start with the Druid List::lens API and the Content enum shown in the issue, then trace how AppData::contents is supplied to the list. Determine how the list can switch among All, Text, and Image views, and verify that the chosen approach supports all three requested content filters.

Written by the indexing model from the issue text.