add docstring for expect_json decorator

common/djangoapps/util/json_request.py

@@ -4,6 +4,11 @@ import json
 
 
 def expect_json(view_function):
+    """
+    View decorator for simplifying handing of requests that expect json.  If the request's
+    CONTENT_TYPE is application/json, parses the json dict from request.body, and updates
+    request.POST with the contents.
+    """
     @wraps(view_function)
     def expect_json_with_cloned_request(request, *args, **kwargs):
         # cdodge: fix postback errors in CMS. The POST 'content-type' header can include additional information