The Body mixin of the Fetch API represents the body of the response/request,
you to declare what its content type is and how it should be

web.fetch interfaces.

The Headers interface of the Fetch API allows you to perform
actions on HTTP request and response headers. These actions include
setting, adding to, and removing. A Headers object has an associated
list, which is initially empty and consists of zero or more name
value pairs. You can add to this using methods like `append()`
Examples.) In all methods of this interface, header names are
by case-insensitive byte sequence.

The ReadableByteStreamController interface of the Streams API
a controller allowing control of a `web.files.ReadableStream`'s
and internal queue. Byte stream controllers are for byte streams.

The ReadableStreamDefaultReader interface of the Streams API
a BYOB (\"bring your own buffer\") reader that can be used to
stream data supplied by the developer (e.g. a custom `ReadableStream.ReadableStream()`

The ReadableStreamBYOBRequest interface of the Streams API represents
pull request into a `web.fetch.ReadableByteStreamController`

The ReadableStreamDefaultController interface of the Streams
represents a controller allowing control of a `web.files.ReadableStream`'s
and internal queue. Default controllers are for streams that
not byte streams.

The ReadableStreamDefaultReader interface of the Streams API
a default reader that can be used to read stream data supplied
a network (e.g. a fetch request).

The Request interface of the Fetch API represents a resource

The Response interface of the Fetch API represents the response
a request.

The WritableStreamDefaultController interface of the the Streams
represents a controller allowing control of a `web.streams.WritableStream`'s
When constructing a WritableStream, the underlying sink is given
corresponding WritableStreamDefaultController instance to manipulate.