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
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
A helper method to dispatch to a AppendToItemField, SetItemField, or
   DeleteItemField
 @param [Hash] update An update of some type