src/vs/editor/common/model/bracketPairsTextModelPart/bracketPairsTree/ast.ts/TwoThreeListAstNode/deepClone
class TwoThreeListAstNode:	public deepClone(): ListAstNode {
		return new TwoThreeListAstNode(
			this.length,
			this.listHeight,
			this._item1.deepClone(),
			this._item2.deepClone(),
			this._item3 ? this._item3.deepClone() : null,
			this.missingOpeningBracketIds
		);
	}