focal_loss = lambda x,y: focal_loss_lgb(x, y, alpha=0.25, gamma=1.)
cv_result = lgb.cv(
	params,
	train,
	num_boost_round=num_boost_round,
	fobj = focal_loss,
	feval = focal_loss_lgb_f1_score,
	nfold=3,
	stratified=True,
	early_stopping_rounds=20)