{
    "num_leaves":{"_type":"randint","_value":[20, 31]},
    "learning_rate":{"_type":"choice","_value":[0.01, 0.05, 0.1, 0.2]},
    "bagging_fraction":{"_type":"uniform","_value":[0.7, 1.0]},
    "bagging_freq":{"_type":"choice","_value":[1, 2, 4, 8, 10]}
}