Fixed #27739 -- Documented LabelCommand.label.

docs/howto/custom-management-commands.txt

@@ -352,6 +352,12 @@ the command line, and does something with each of them.
 Rather than implementing :meth:`~BaseCommand.handle`, subclasses must implement
 :meth:`~LabelCommand.handle_label`, which will be called once for each label.
 
+.. attribute:: LabelCommand.label
+
+    A string describing the arbitrary arguments passed to the command. The
+    string is used in the usage text and error messages of the command.
+    Defaults to ``'label'``.
+
 .. method:: LabelCommand.handle_label(label, **options)
 
     Perform the command's actions for ``label``, which will be the string as