added argument to %call tag example

doc/build/content/defs.txt

diff --git a/doc/build/content/defs.txt b/doc/build/content/defs.txt
index 05d4b0e..d2212a0 100644
--- a/doc/build/content/defs.txt
+++ b/doc/build/content/defs.txt
@@ -179,7 +179,7 @@
         </table>
     </%def>
     
-    <%call expr="layoutdata([[1,2,3],[4,5,6],[7,8,9]])">
+    <%call expr="layoutdata([[1,2,3],[4,5,6],[7,8,9]])" args="col">
         Body data: ${col}
     </%call>