Demonstration of hidden class ParameterGrid on sklearn.

ParameterGrid_test.py

from sklearn.model_selection._search import ParameterGrid

param_grid = {
    "metric_list" : [None, "None", "binary_logloss", "auc", ["binary_logloss"], ["auc"], 
                    ['binary_logloss','auc', ], ['auc', 'binary_logloss',] ],
    "first_metric_only": [True, False],
    "eval_train_metric": [True, False],
}
pg = ParameterGrid(param_grid)

# displaying all pattern of the parameter combination.
for p in pg:
    print(p)