v1.9.0

MLJModelInterface v1.9.0

Diff since v1.8.0

Closed issues:

• Interface broken (#171)
• Add a method params2 to recursively convert a model to a nested named tuple (#176)

Merged pull requests:

• remove misleading descr used in doc_header docstring (#172) (@OkonSamuel)
• Adding flat_params function (#177) (@pebeto)