armor-statues/data/armor_statues/predicates/savedpose_mainhand.json

{
  "condition": "minecraft:entity_properties",
  "entity": "this",
  "predicate": {
    "equipment": {
      "mainhand": {
        "items": ["minecraft:written_book"],
	    "nbt": "{datapack:ArmorStatuesV2, SavedPose:{} }"
      }
    }
  }
}