Revert "make centroid indices attribute"

This reverts commit 02857e6.

qsprpred/data/chem/clustering.py

@@ -213,15 +213,15 @@ def _get_centroids(self, fps: list) -> list:
         """
         self._set_nClusters(len(fps))
         picker = rdSimDivPickers.MaxMinPicker()
-        self.centroid_indices = picker.LazyBitVectorPick(
+        centroid_indices = picker.LazyBitVectorPick(
             fps,
             len(fps),
             self.nClusters,
             firstPicks=self.initialCentroids if self.initialCentroids else [],
             seed=self.seed if self.seed is not None else -1,
         )
 
-        return self.centroid_indices
+        return centroid_indices
 
 
 class FPSimilarityLeaderPickerClusters(FPSimilarityClusters):
@@ -247,8 +247,8 @@ def _get_centroids(self, fps: list) -> list:
         Get cluster centroids with LeaderPicker algorithm.
         """
         picker = rdSimDivPickers.LeaderPicker()
-        self.centroid_indices = picker.LazyBitVectorPick(
+        centroid_indices = picker.LazyBitVectorPick(
             fps, len(fps), self.similarityThreshold
         )
 
-        return self.centroid_indices
+        return centroid_indices