"create ate document" to "create a document"

Author: symroe

source/use-cases/category-hierarchy.txt

@@ -131,7 +131,7 @@ define this array, consider the following helper function:
 
 You only need to travel "up" one level in the hierarchy to get the
 ancestor list for "Ragtime" that you can use to build the ancestor
-list for "Swing." Then create ate document with the following set of
+list for "Swing." Then create a document with the following set of
 operations:
 
 .. code-block:: python