[plotting] Fix the random grouping option

bob/fusion/base/tools/plotting.py

 #!/usr/bin/env python
 
-import numpy
 import bob.learn.em
+import numpy as np
+from numpy.random import default_rng
 
 
-def grouping(scores, gformat='random', npoints=500, seed=None, **kwargs):
+def grouping(scores, gformat="random", npoints=500, seed=None, **kwargs):
 
-    scores = numpy.asarray(scores)
+    scores = np.asarray(scores)
     if scores.size == 0:
         return scores
 
-    if(gformat == "kmeans"):
+    if gformat == "kmeans":
         kmeans_machine = bob.learn.em.KMeansMachine(npoints, 2)
         kmeans_trainer = bob.learn.em.KMeansTrainer()
         bob.learn.em.train(
-            kmeans_trainer, kmeans_machine, scores, max_iterations=500,
-            convergence_threshold=0.1)
+            kmeans_trainer,
+            kmeans_machine,
+            scores,
+            max_iterations=500,
+            convergence_threshold=0.1,
+        )
         scores = kmeans_machine.means
 
-    elif(gformat == "random"):
-        if seed is not None:
-            numpy.random.seed(seed)
-        scores_indexes = numpy.array(
-            numpy.random.rand(npoints) * scores.shape[0], dtype=int)
-
-        scores = scores[scores_indexes]
+    elif gformat == "random":
+        rng = default_rng(seed)
+        scores = rng.choice(scores, npoints, replace=False)
 
     return scores