BTBSession crashes when record is not performed.

[pvk-developer]

• BTB version: 0.3.5
• Python version: 3.6
• Operating System: Ubuntu 18.04

Description

When runing a BTBSession with a Tunable({}) this will fail to record the score obtained with the "default" configuration of {}.

This case is an unusual one as the object Tunable without hyperparameters to tune shouldn't exist, however, during research on tuning hyperparameters of pipelines, we have faced this problem when there was no tunable hyperparameters on the pipeline.

Solution propose

We noticed that the cardinality is 1. In this case, the Tuner for that Tunable shouldn't be instantiated, tuner = None and then when attempts to record simply check that the selected tuner is not None.