ENH: Add visualization to python package

python-package/xgboost/__init__.py

@@ -8,9 +8,11 @@ from __future__ import absolute_import
 from .core import DMatrix, Booster
 from .training import train, cv
 from .sklearn import XGBModel, XGBClassifier, XGBRegressor
+from .plotting import plot_importance, plot_tree, to_graphviz
 
 __version__ = '0.4'
 
 __all__ = ['DMatrix', 'Booster',
            'train', 'cv',
-           'XGBModel', 'XGBClassifier', 'XGBRegressor']
+           'XGBModel', 'XGBClassifier', 'XGBRegressor',
+           'plot_importance', 'plot_tree', 'to_graphviz']