fixed a bug with NoneType

cdplib/pipeline_selector/PipelineSelector.py

@@ -231,7 +231,7 @@ class PipelineSelector(ABC):
             during cross-validation
             example: [([0,1,2], [3,4]), ([1,2,3], [4,5])]
         '''
-        NoneType = None.__classe__
+        NoneType = None.__class__
 
         input_err = "Non-valid combination of train and val data types"