При попытке использовать Dmatrix ошибка: "AttributeError: 'DMatrix' object has no attribute 'items'"

При попытке использовать Dmatrix в xgboost.cv:

params = {
    'num_boost_round': 500,
    'max_depth': 4,
    'min_child_weight': 2,
    'subsample': 0.8,
    'colsample_bytree': 0.5,
    'eta':0.05}


X_train = np.random.random(size=(100, 1000))
y_train = np.random.random(size=(100, 1))
dtrain = xgboost.DMatrix(X_train,label = y_train)
rescv = xgboost.cv(dtrain,params,nfold=5,metrics = 'precision',early_stopping_rounds=20)

Выводит ошибку:

AttributeErrorTraceback (most recent call last) <ipython-input-86-96544cdc772c> in <module>()
     10 y_train = np.random.random(size=(100, 1))
     11 dtrain = xgboost.DMatrix(X_train,label = y_train)
---> 12 rescv = xgboost.cv(dtrain,params,nfold=5,metrics = 'precision',early_stopping_rounds=20)
     13 

C:\ProgramData\Anaconda2\lib\site-packages\xgboost\training.pyc in cv(params, dtrain, num_boost_round, nfold, stratified, folds, metrics, obj, feval, maximize, early_stopping_rounds, fpreproc, as_pandas, verbose_eval, show_stdv, seed, callbacks, shuffle)
    401             params['eval_metric'] = _metrics
    402     else:
--> 403         params = dict((k, v) for k, v in params.items())
    404 
    405     if len(metrics) == 0 and 'eval_metric' in params:

AttributeError: 'DMatrix' object has no attribute 'items'