# Add a `key` in the tree
	fun add(key: String) do
		var root = self.root
		if root == null then
			self.root = new BKNode(key)
			return
		end

		var node = root
		var dist = node.key.levenshtein_distance(key)

		while node.has_key(dist) do
			if dist == 0 then return
			node = node[dist]
			dist = node.key.levenshtein_distance(key)
		end
		node[dist] = new BKNode(key)
	end