support for displaying tuned hyperparameters

[hirzel]

After running an optimizer for joint operator selection and hyperparameter tuning, users typically want to display the results of that tuning. To see the tuned hyperparameters, in Lale, users typically call pretty_print. This prints out Python code for re-creating that exact pipeline, as demonstrated in this notebook.

A first solution would be to simply wrap Lale's pretty-print method in Julia. However, that would print Python code, and it would be nicer to print Julia code instead. So a second solution could be to make the existing pretty-print method more general, perhaps with another supported value for the as_type argument, so users can write pretty_print(as_type="julia"). A third solution could be to re-implement the pretty-print method for Julia in Julia, probably starting from the result of the to_json method. For either the second or the third option, it would be great to have good test coverage, along the lines of the Python pretty-print tests.

[ppalmes]

pretty_print ipython_display does not render in julia notebook. it seems that it is specific to ipython interpreter.