code: def dispatch_update_type!(update)
        type = update.keys.first
        upd  = update[type]
        case type
        when :append_to_item_field
          append_to_item_field!(upd)
        when :set_item_field
          set_item_field!(upd)
        when :delete_item_field
          delete_item_field!(upd)
        else
          raise EwsBadArgumentError, "Bad Update type. #{type}"
        end
      end
docs: A helper method to dispatch to a AppendToItemField, SetItemField, or
     DeleteItemField
   @param [Hash] update An update of some type