Enable tab completion after dictionary value

This is an enhancement, that I would like to use in jupyterlab, but i guess it has to be implemented in ipython.
I often have complex dict structures and this would help me.
Basically I want
```
dictionary['key']
dictionary['key']['
dictionary['key'].
```
to work like if i would do
```
value = dictionary['key']
value
value['
value.
```
What actually happens is, that I get suggestions from global vars or nothing.