feat(core): implement get_params() API for steps

[deepyaman]

Description of changes

For example, from the example notebook:

import ibis_ml as ml

flights_rec = ml.Recipe(
    ml.ExpandDate("date", components=["dow", "month"]),
    ml.Drop("date"),
    ml.TargetEncode(ml.nominal()),
    ml.DropZeroVariance(ml.everything()),
    ml.MutateAt("dep_time", ibis._.hour() * 60 + ibis._.minute()),
    ml.MutateAt(ml.timestamp(), ibis._.epoch_seconds()),
    # By default, PyTorch requires that the type of `X` is `np.float32`.
    # https://discuss.pytorch.org/t/mat1-and-mat2-must-have-the-same-dtype-but-got-double-and-float/197555/2
    ml.Cast(ml.numeric(), "float32"),
)
flights_rec.get_params()

will yield:

{'steps': (ExpandDate(cols(('date',)), components=['dow', 'month']),
  Drop(cols(('date',))),
  TargetEncode(nominal(), smooth=0.0),
  DropZeroVariance(everything(), tolerance=0.0001),
  MutateAt(cols(('dep_time',)), ((_.hour() * 60) + _.minute())),
  MutateAt(timestamp(), _.epoch_seconds()),
  Cast(numeric(), 'float32')),
 'expanddate': ExpandDate(cols(('date',)), components=['dow', 'month']),
 'drop': Drop(cols(('date',))),
 'targetencode': TargetEncode(nominal(), smooth=0.0),
 'dropzerovariance': DropZeroVariance(everything(), tolerance=0.0001),
 'mutateat-1': MutateAt(cols(('dep_time',)), ((_.hour() * 60) + _.minute())),
 'mutateat-2': MutateAt(timestamp(), _.epoch_seconds()),
 'cast': Cast(numeric(), 'float32'),
 'expanddate__components': ['dow', 'month'],
 'expanddate__inputs': cols(('date',)),
 'drop__inputs': cols(('date',)),
 'targetencode__inputs': nominal(),
 'targetencode__smooth': 0.0,
 'dropzerovariance__inputs': everything(),
 'dropzerovariance__tolerance': 0.0001,
 'mutateat-1__expr': ((_.hour() * 60) + _.minute()),
 'mutateat-1__inputs': cols(('dep_time',)),
 'mutateat-1__named_exprs': {},
 'mutateat-2__expr': _.epoch_seconds(),
 'mutateat-2__inputs': timestamp(),
 'mutateat-2__named_exprs': {},
 'cast__dtype': Float32(nullable=True),
 'cast__inputs': numeric()}

Further down pipe.get_params() would also work:

{'memory': None,
 'steps': [('flights_rec',
   Recipe(ExpandDate(cols(('date',)), components=['dow', 'month']),
          Drop(cols(('date',))),
          TargetEncode(nominal(), smooth=0.0),
          DropZeroVariance(everything(), tolerance=0.0001),
          MutateAt(cols(('dep_time',)), ((_.hour() * 60) + _.minute())),
          MutateAt(timestamp(), _.epoch_seconds()),
          Cast(numeric(), 'float32'))),
  ('mod',
   <class 'skorch.classifier.NeuralNetClassifier'>[uninitialized](
     module=<class '__main__.MyModule'>,
   ))],
 'verbose': False,
 'flights_rec': Recipe(ExpandDate(cols(('date',)), components=['dow', 'month']),
        Drop(cols(('date',))),
        TargetEncode(nominal(), smooth=0.0),
        DropZeroVariance(everything(), tolerance=0.0001),
        MutateAt(cols(('dep_time',)), ((_.hour() * 60) + _.minute())),
        MutateAt(timestamp(), _.epoch_seconds()),
        Cast(numeric(), 'float32')),
 'mod': <class 'skorch.classifier.NeuralNetClassifier'>[uninitialized](
   module=<class '__main__.MyModule'>,
 ),
 'flights_rec__steps': (ExpandDate(cols(('date',)), components=['dow', 'month']),
  Drop(cols(('date',))),
  TargetEncode(nominal(), smooth=0.0),
  DropZeroVariance(everything(), tolerance=0.0001),
  MutateAt(cols(('dep_time',)), ((_.hour() * 60) + _.minute())),
  MutateAt(timestamp(), _.epoch_seconds()),
  Cast(numeric(), 'float32')),
 'flights_rec__expanddate': ExpandDate(cols(('date',)), components=['dow', 'month']),
 'flights_rec__drop': Drop(cols(('date',))),
 'flights_rec__targetencode': TargetEncode(nominal(), smooth=0.0),
 'flights_rec__dropzerovariance': DropZeroVariance(everything(), tolerance=0.0001),
 'flights_rec__mutateat-1': MutateAt(cols(('dep_time',)), ((_.hour() * 60) + _.minute())),
 'flights_rec__mutateat-2': MutateAt(timestamp(), _.epoch_seconds()),
 'flights_rec__cast': Cast(numeric(), 'float32'),
 'flights_rec__expanddate__components': ['dow', 'month'],
 'flights_rec__expanddate__inputs': cols(('date',)),
 'flights_rec__drop__inputs': cols(('date',)),
 'flights_rec__targetencode__inputs': nominal(),
 'flights_rec__targetencode__smooth': 0.0,
 'flights_rec__dropzerovariance__inputs': everything(),
 'flights_rec__dropzerovariance__tolerance': 0.0001,
 'flights_rec__mutateat-1__expr': ((_.hour() * 60) + _.minute()),
 'flights_rec__mutateat-1__inputs': cols(('dep_time',)),
 'flights_rec__mutateat-1__named_exprs': {},
 'flights_rec__mutateat-2__expr': _.epoch_seconds(),
 'flights_rec__mutateat-2__inputs': timestamp(),
 'flights_rec__mutateat-2__named_exprs': {},
 'flights_rec__cast__dtype': Float32(nullable=True),
 'flights_rec__cast__inputs': numeric(),
 'mod__module': __main__.MyModule,
 'mod__criterion': torch.nn.modules.loss.NLLLoss,
 'mod__optimizer': torch.optim.sgd.SGD,
 'mod__lr': 0.1,
 'mod__max_epochs': 10,
 'mod__batch_size': 128,
 'mod__iterator_train': torch.utils.data.dataloader.DataLoader,
 'mod__iterator_valid': torch.utils.data.dataloader.DataLoader,
 'mod__dataset': skorch.dataset.Dataset,
 'mod__train_split': <skorch.dataset.ValidSplit object at 0x31cbccad0>,
 'mod__callbacks': None,
 'mod__predict_nonlinearity': 'auto',
 'mod__warm_start': False,
 'mod__verbose': 1,
 'mod__device': 'cpu',
 'mod__compile': False,
 'mod__use_caching': 'auto',
 'mod___params_to_validate': {'iterator_train__shuffle'},
 'mod__iterator_train__shuffle': True,
 'mod__classes': None,
 'mod__callbacks__epoch_timer': <skorch.callbacks.logging.EpochTimer at 0x15fc20690>,
 'mod__callbacks__train_loss': <skorch.callbacks.scoring.PassthroughScoring at 0x31c67ce50>,
 'mod__callbacks__train_loss__name': 'train_loss',
 'mod__callbacks__train_loss__lower_is_better': True,
 'mod__callbacks__train_loss__on_train': True,
 'mod__callbacks__valid_loss': <skorch.callbacks.scoring.PassthroughScoring at 0x31c7c47d0>,
 'mod__callbacks__valid_loss__name': 'valid_loss',
 'mod__callbacks__valid_loss__lower_is_better': True,
 'mod__callbacks__valid_loss__on_train': False,
 'mod__callbacks__valid_acc': <skorch.callbacks.scoring.EpochScoring at 0x1499f68d0>,
 'mod__callbacks__valid_acc__scoring': 'accuracy',
 'mod__callbacks__valid_acc__lower_is_better': False,
 'mod__callbacks__valid_acc__on_train': False,
 'mod__callbacks__valid_acc__name': 'valid_acc',
 'mod__callbacks__valid_acc__target_extractor': <function skorch.utils.to_numpy(X)>,
 'mod__callbacks__valid_acc__use_caching': True,
 'mod__callbacks__print_log': <skorch.callbacks.logging.PrintLog at 0x31cbbfc50>,
 'mod__callbacks__print_log__keys_ignored': None,
 'mod__callbacks__print_log__sink': <function print(*args, sep=' ', end='\n', file=None, flush=False)>,
 'mod__callbacks__print_log__tablefmt': 'simple',
 'mod__callbacks__print_log__floatfmt': '.4f',
 'mod__callbacks__print_log__stralign': 'right'}

Issues closed

Partially addresses #135

Will probably leave it open until address set_params(), too

[deepyaman]

I don't love that I have to override this, but I guess it's better to do this for now (rather than change the API to require specifying expressions in a dictionary).

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 89.28571% with 3 lines in your changes missing coverage. Please review.

Project coverage is 85.53%. Comparing base (aa71647) to head (0387595).

Files with missing lines	Patch %	Lines
ibis_ml/core.py	85.71%	2 Missing ⚠️
ibis_ml/steps/_common.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
+ Coverage   85.24%   85.53%   +0.29%     
==========================================
  Files          27       27              
  Lines        1938     1964      +26     
==========================================
+ Hits         1652     1680      +28     
+ Misses        286      284       -2     

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[deepyaman]

Alternatively, I guess can just get rid of this whole if block? A Step can't be nested in another Step—at least for now.

Probably better...

Lines 366–7 aren't currently being hit, and I don't see any reasonable way it would be hit.

[deepyaman]

This validation won't get hit unless you don't override _get_param_names for a step with varargs in the constructor (e.g. Mutate or MutateAt. I suppose I can add a test for malformed custom step?

[jitingxu1]

It looks great to me. Feel free to merge it on your own.