DOC add example in docstring of silhouette_score (scikit-learn#28125)

Co-authored-by: Guillaume Lemaitre <[email protected]>

sklearn/metrics/cluster/_unsupervised.py

@@ -119,6 +119,16 @@ def silhouette_score(
 
  .. [2] `Wikipedia entry on the Silhouette Coefficient
  <https://en.wikipedia.org/wiki/Silhouette_(clustering)>`_
+
+ Examples
+ --------
+ >>> from sklearn.datasets import make_blobs
+ >>> from sklearn.cluster import KMeans
+ >>> from sklearn.metrics import silhouette_score
+ >>> X, y = make_blobs(random_state=42)
+ >>> kmeans = KMeans(n_clusters=2, random_state=42)
+ >>> silhouette_score(X, kmeans.fit_predict(X))
+ 0.49...
  """
  if sample_size is not None:
  X, labels = check_X_y(X, labels, accept_sparse=["csc", "csr"])