Description:
This is an SKSE Plugin, which adds new native functions to papyrus.

Requirements:
-SKSE 1.7.0 or newer

Added Functions:
Related to inventorys:

• GetNumItemsWithKeyword(ObjectReference objRef, Keyword key)
• GetNthFormWithKeyword(ObjectReference objRef, Keyword key, int KeywordIndex)
• GetTotalNumItemsWithKeyword(ObjectReference objRef, Keyword key)
• GetTotalNumItems(ObjectReference objRef)

Related to poisons:

• Worn_PoisonWeapon(Actor akActor, int handSlot, Potion poison, int Charges)
• Worn_IsWeaponPoisoned(Actor akActor, int handSlot)
• Worn_GetPoison(Actor akActor, int handSlot)
• Worn_GetPoisonCharges(Actor akActor, int handSlot)
• Worn_SetPoisonCharges(Actor akActor, int handSlot, int Charges = 1)
• SetPoisonCharges(ObjectReference objRef, int Charges = 1)
• PoisonWeapon(ObjectReference objRef, Potion poison, int Charges)
• GetPoison(ObjectReference objRef)
• SetPoisonCharge(ObjectReference objRef, int Charges)
• IsWeaponPoisoned(ObjectReference objRef)

Example code:
import _Q2C_Functions
ObjectReference Property PlayerRef Auto
Keyword Property VendorItemPotion Auto

Function ReWeightPotions()
int PotionIndex = GetNumItemsWithKeyword(PlayerRef, VendorItemPotion)
While(PotionIndex > 0)
PotionIndex -= 1
Form potion = GetNthFormWithKeyword(PlayerRef, VendorItemPotion, PotionIndex)
potion.SetWeight(0.0)
endWhile
endFunction

Feel free to package this plugin with your own mods and use it for your own projects.
Please just mention me in a footnote somewhere.

All Credits are going to the SKSE Team!