Modding Help help in treasure pool

how can i make that i will get a specific item for sure and the other by chance?

 

This is an example from the common.treasurepool file

Code:

"weaponChestTreasure" : [
    [0, {
      "fill" : [
        {"pool" : "goodWeapon"}
      ],
      "poolRounds" : [
        [0.5, 2],
        [0.3, 3],
        [0.2, 4]
      ],
      "pool" : [
        {"weight" : 1.0, "pool" : "basicTreasure"}
      ]
    }]
  ]

Fill is a guaranteed item/pool
Pool is a pool of items

so in this example, it 100% gives a weapon from the goodWeapon treasure pool and then adds some stuff from the basicTreasure pool