code: func (r Virtual_Guest) GetUpgradeItemPrices(includeDowngradeItemPrices *bool) (resp []datatypes.Product_Item_Price, err error) {
  	params := []interface{}{
  		includeDowngradeItemPrices,
  	}
  	err = r.Session.DoRequest("SoftLayer_Virtual_Guest", "getUpgradeItemPrices", params, &r.Options, &resp)
  	return
  }
docs: // getUpgradeItemPrices() retrieves a list of all upgrades available to a CloudLayer Computing Instance. Upgradeable items include, but are not limited to, number of cores, amount of RAM, storage configuration, and network port speed.
  //
  // This method exclude downgrade item prices by default. You can set the "includeDowngradeItemPrices" parameter to true so that it can include downgrade item prices.