src/vs/editor/common/model/guidesTextModelPart.ts/GuidesTextModelPart/_computeIndentLevel
class GuidesTextModelPart:	private _computeIndentLevel(lineIndex: number): number {
		return computeIndentLevel(
			this.textModel.getLineContent(lineIndex + 1),
			this.textModel.getOptions().tabSize
		);
	}