ENH: added comment on missing value imputation.

OBIA/OBIABase.py

@@ -319,6 +319,7 @@ class OBIABase:
         for tilenum in self.tiles.keys():
             tile_data = self.get_full_stats_on_tile(tilenum)
             L = tile_data.index.to_numpy(dtype=np.int32)
+            # Probably sub-optimal and error-prone, uses mean value from tile only 
             imp = SimpleImputer(missing_values=np.nan, strategy='mean')
             X = imp.fit_transform(tile_data[vars].to_numpy())
             if normalize is not None: