def build_grouping_body
      arr = []
      data.each do |_,group|                     
        arr << render_group(group, options)
      end
      output << arr.join(",\n")
    end
def build_grouping_body
      arr = []
      data.each do |_,group|                     
        arr << render_group(group, options)
      end
      output << arr.join(",\n")
    end
Generates the body for a grouping. Iterates through the groups and
 renders them using the group controller.