input cells options to be dynamically populated

Hi team, great job on adding the input cells functionnality, this is great. 

We've been heavily relying on ipywidgets in Jupyter notebooks to create dropdown lists for clients to filter results based on their data content. However, creating the input cells variable options manually is not very useful ... we use them in Jupyter to filter, for instance, the bottom 10 or top 10 entries in a dataset that gets updated all the time - creating these lists manually is not going to work.

Would you consider adding this extra layer to allow us to pass a function to create dynamically the dropdow lists variable options ? Just like it is possible in Jupyter ?

This is we proceed with ipywidgets for instance at the moment using a dynamic list from a pandas dataframe:

dropdown_widget = Dropdown(options = dataframe['my_options_column'].unique().tolist(), description ='Select option')

Many thanks and keep up the good work !