Add experiment.get_image_logs()

Currently there is no way to download images uploaded by log_image. Please return urls or ids to download, for example exp.download_image_log(exp.get_image_logs()['id']) .

Also get_text_logs(), optionally with dataframe. optuna-contrib logs hyperparams to text, so it is neccessary to get best_parameters_so_far (before complete)

note

Originally posted on spectrum on Jun 6, 2020, migrated here on Jun 9, 2020.