query

        pub fn query(self: HuffmanTree, index: usize, prefix: u16) error{HuffmanTreeIncomplete}!Result {
            var node = self.nodes[index];
            const weight = node.weight;
            var i: usize = index;
            while (node.weight == weight) {
                if (node.prefix == prefix) return .{ .symbol = node.symbol };
                if (i == 0) return error.HuffmanTreeIncomplete;
                i -= 1;
                node = self.nodes[i];
            }
            return .{ .index = i };
        }