Removed NoneType from code

NoneType is no longer directly importable in newer versions of python

src/brush/estimator.py

@@ -12,7 +12,6 @@
 # import deap as dp
 from deap import algorithms, base, creator, tools
 # from tqdm import tqdm
-from types import NoneType
 from sklearn.metrics import average_precision_score
 from sklearn.preprocessing import MinMaxScaler
 import _brush
@@ -404,7 +403,7 @@ def _make_data(self, X, y=None, feature_names=[], validation_size=0.0):
 
         assert isinstance(X, np.ndarray)
 
-        if isinstance(y, NoneType):
+        if isinstance(y, None):
             return _brush.Dataset(X=X,
                     feature_names=feature_names, validation_size=validation_size)
 
@@ -605,4 +604,4 @@ def _make_individual(self):
 
 #     def transform(self, X):
 #         """Transform X using the best estimator in the archive. """
-#         return self.predict(X)
+#         return self.predict(X)