def add(partial_name, *args)
      workbook.partials.get(partial_name).tap do |p|
        instance_exec(*args, &p) if p
      end
    end
def add(partial_name, *args)
      workbook.partials.get(partial_name).tap do |p|
        instance_exec(*args, &p) if p
      end
    end
add partials to dynamically add markup to your workbook
 note: you can also define element templates to add element specific
 markup to your workbook