Returns a collection containing the element specified by the array index. Negative numbers are counted backwards from the end of the collection.
var beatles = Pablo([
Pablo.circle({id:'john'}),
Pablo.circle({id:'paul'}),
Pablo.circle({id:'george'}),
Pablo.circle({id:'ringo'})
]);
alert(beatles.eq(2).attr('id')); // 'george'
alert(beatles.eq(-1).attr('id')); // 'ringo'