v0.2.9 Release

• Revamped Metric API
  • Metrics now return Result type for data fetching methods. This allows metrics to encode exceptions encountered during fetching into their returned value so Ax can defer their raising.
    • Call experiment.fetch_data_results to access these Results (organized by trial index and metric name) on the Experiment level.
      • experiment.fetch_data still returns Data directly by unwrapping the results under the hood for backwards compatibility considerations.
    • To update your existing custom Metrics you must wrap the return value of fetch_trial_data with Ok.
      • See the Scheduler tutorial for an example
• Improvements to Scheduler Exception handling via Results
  • If an Exception is encountered by the Scheduler during data fetching, either mark the trial as FAILED or continue the optimization (while alerting the user) depending on the failed metric’s role in the optimization. See scheduler.py for exact rules.
• SAASBO memory utilization improvements
• Miscellaneous bugfixes