src/vs/workbench/browser/parts/editor/editorActions.ts/CloseLeftEditorsInGroupAction/getTarget
class CloseLeftEditorsInGroupAction:	private getTarget(context?: IEditorIdentifier): { editor: EditorInput | null; group: IEditorGroup | undefined } {
		if (context) {
			return { editor: context.editor, group: this.editorGroupService.getGroup(context.groupId) };
		}

		// Fallback to active group
		return { group: this.editorGroupService.activeGroup, editor: this.editorGroupService.activeGroup.activeEditor };
	}