DOC: Improve code example for Index.get_indexer (pandas-dev#21511)

Author: topper-123

pandas/core/indexes/base.py

@@ -3148,17 +3148,22 @@ def droplevel(self, level=0):
 
             .. versionadded:: 0.21.0 (list-like tolerance)
 
-        Examples
-        --------
-        >>> indexer = index.get_indexer(new_index)
-        >>> new_values = cur_values.take(indexer)
-
         Returns
         -------
         indexer : ndarray of int
             Integers from 0 to n - 1 indicating that the index at these
             positions matches the corresponding target values. Missing values
             in the target are marked by -1.
+
+        Examples
+        --------
+        >>> index = pd.Index(['c', 'a', 'b'])
+        >>> index.get_indexer(['a', 'b', 'x'])
+        array([ 1,  2, -1])
+
+        Notice that the return value is an array of locations in ``index``
+        and ``x`` is marked by -1, as it is not in ``index``.
+
         """
 
     @Appender(_index_shared_docs['get_indexer'] % _index_doc_kwargs)