Request for explanation about the origin of some elements

[raphael10-collab]

I do not understand where some elements come from:

Where do Transform and TransformCallback come from? https://github.com/automerge/pushpin/blob/master/src/apps/clipper-host/NativeMessaging.ts

I didn't find them in https://developer.mozilla.org/en-US/docs/Web/API/TransformStream.
I found TransformerTransformCallback in the Streams Specs: https://streams.spec.whatwg.org/#callbackdef-transformertransformcallback but no references in Mozilla Docs.

Are Stream node's stream?
In https://github.com/automerge/pushpin/blob/master/src/renderer/hyperfile.ts#L2 for example we find "Readable" from 'stream'
but I do not fine Stream in node's API:
https://nodejs.org/api/stream.html#stream_class_stream_readable

Can you please help me to clarify?

Where the type BeforeUnloadEvent come from? https://github.com/automerge/pushpin/blob/master/src/freeze-dry-preload/index.ts#L37

Where DetailedHTMLProps come from? https://github.com/automerge/pushpin/blob/master/src/background/components/Card.tsx#L3

background/components/List.tsx:type Props = React.DetailedHTMLProps<React.HTMLAttributes<HTMLDivElement>, 
HTMLDivElement>
background/components/Card.tsx:type Props = React.DetailedHTMLProps<React.HTMLAttributes<HTMLDivElement>, 
HTMLDivElement>

I found this: https://github.com/automerge/pushpin/blob/master/src/background/components/Expandable.tsx#L11 but maybe it's a different thing

renderItems : https://github.com/automerge/pushpin/blob/master/src/background/components/LimitedList.tsx#L16

5. https://github.com/automerge/pushpin/blob/master/src/renderer/components/content-types/workspace/Authors.tsx#L34
   What are id, i and a ?