javascript - In the tabpanel of ExtJS 4, how to create parent tab includes 2 child tab -

i have 2 parent tabs, each tab includes 2 child tab. pls see picture more detail:

how create group tab parent tab , when author click parent tab, child tab shown. thanks

ext.widget('tabpanel', {     width: 500,     activetab: 0,     items: [{         title: 'parent tab 1',         items : [             ext.widget('tabpanel', {                 activetab: 0,                  items : [{                     title: 'child tab 1',                     bodypadding: 10,                     html : "my content of child tab 1 here"                 },{                     title: 'child tab 2',                     bodypadding: 10,                     html : "my content of child tab 2 here"                 }]             })         ]     },{         title: 'parent tab 2',         bodypadding: 10,         html : "parent tab 2 content here without child tabs"     }] }); 

here fiddle example of parent tab containg child tabs :

http://jsfiddle.net/q7f5q/200/

hope looking for.