See documentation in docs/topics/shell.rst
|Wrap a request inside a Deferred.
|Open a shell to inspect the given response
Wrap a request inside a Deferred.
This function is harmful, do not use it until you know what you are doing.
This returns a Deferred whose first pair of callbacks are the request callback and errback. The Deferred also triggers when the request callback/errback is executed (i.e. when the request is downloaded)
WARNING: Do not call request.replace() until after the deferred is called.