Estimators inside parameter grid don't work

[Yatoom]

When I use GridSearchCV or RandomizedSearchCV with a param grid that includes a list of estimators, this will raise a TypeError: TypeError(repr(o) + " is not JSON serializable"). This happens inside the _extract_information_from_model() method.

Here is the code to reproduce this error:

import openml
from sklearn.ensemble import AdaBoostClassifier
from sklearn.model_selection import GridSearchCV
from sklearn.tree import DecisionTreeClassifier, ExtraTreeClassifier

task = openml.tasks.get_task(49)

param_grid = {
    "base_estimator": [DecisionTreeClassifier(), ExtraTreeClassifier()]
}

clf = GridSearchCV(AdaBoostClassifier(), param_grid=param_grid)
run = openml.runs.run_task(task, clf)
run.publish()

[mfeurer]

Thanks for reporting. This is an inteded limitation. We did not yet implement this feature as we want to spend our time getting the basic functionality of package running there first.

[janvanrijn]

Created a unit test for this, as it might be useful to check this behaviour holds and does not flood the database with invalid runs. PR will follow.