Shift + Tab signature hinting?

Coming from a Python-in-Jupyter background, I notice that `Tab` works as you would expect (reveals all available methods/attributes), but `Shift+Tab` (signature hinting) does not. I could not find documentation on this. Is `Shift+Tab` not supported, or is my setup is incorrect?

Example:
```
type Foo struct {
name string
description string
}
func (f Foo) Qux(s string) string {
return s
}
n := Foo{"bar", "baz"}
```

* `n. + Tab` Works as expected -> shows dropdown list: `name, description`
* `n.Qux( + Tab` Does not work as expected -> does not show anything and logs in Terminal: `Unhandled shell message: inspect_request`

My setup:
```
$ jupyter --version
4.4.0

$ uname -v
Darwin Kernel Version 17.7.0: Wed Apr 24 21:17:24 PDT 2019; root:xnu-4570.71.45~1/RELEASE_X86_64

$ brew list --versions zeromq
zeromq 4.3.1_1
```