Functions
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node_damage.damage(pos, node, digger, num)
	--Give damage to this node, and set it into the next stage of cracking.
	--For reference, there are four stages in total, including the stage without damage at all.
	--When the highest stage is damaged, the nodes is finally destroyed, and the node is either given to the player who destroyed it,
	--or left on the ground.
	pos: The location of the node to damage
	node: The node itself to damage. This is optional. It can be provided if available, but this function can get the node itself.
	digger: Optional; the person who is damaging this node. Used to determine protection permission.
	num: Optional; the amount of times to damage this node. If its 3 or more, the node will always be destroyed.
	--Returns a boolean indicating success.

node_damage.repair(pos, node, fixer, num)
	--Remove damage from this node, and set it into the previous stage of cracking.
	--For reference, there are four stages in total, including the stage without damage at all.
	--If the node is already fully repaired, nothing will happen.
	pos: The location of the node to repair
	node: The node itself to damage. This is optional. It can be provided if available, but this function can get the node itself.
	fixer: Optional; A person (ObjectRef) who is repairing this node. Used to determine protection permission.
	num: Optional; the amount of times to repair this node. If its 3 or more, the node will always be fully repaired.
	--Returns a boolean indicating success.