public IInventory getCellUpgradeInventory()
{
if ( cacheUpgrades == null )
{
ICellWorkbenchItem cell = getCell();
if ( cell == null )
return null;
ItemStack is = this.cell.getStackInSlot( 0 );
if ( is == null )
return null;
IInventory inv = cell.getUpgradesInventory( is );
if ( inv == null )
return null;
return cacheUpgrades = inv;
}