Merge pull request matplotlib#19415 from dstansby/array-example

DOC: Make TaggedValue in basic_units a sequence

Author: tacaswell

examples/units/basic_units.py

@@ -154,6 +154,9 @@ def __str__(self):
     def __len__(self):
         return len(self.value)
 
+    def __getitem__(self, key):
+        return TaggedValue(self.value[key], self.unit)
+
     def __iter__(self):
         # Return a generator expression rather than use `yield`, so that
         # TypeError is raised by iter(self) if appropriate when checking for