How can I fix type does not exist error

export interface TaskBase extends CamelCase<BlueprintChecklistInsert> {
    errorMessage?: string;
}

export interface TasksParent extends Omit<TaskBase, 'parent_id'> {
    children: TaskBase[];
}

type BlueprintChecklistInsert = BluePrintCheckList['Insert'];
type BluePrintCheckListGet = BluePrintCheckList['Row'];
const sanatizeUpdatChecklistValueToDb = (values: TasksParent[] | TaskBase[]): BlueprintChecklistInsert[] => {
    const checklists: BlueprintChecklistInsert[] = [];
    values.forEach((el) => {
        const toCamelCase = objectToSnake(el);
        checklists.push(toCamelCase);

        if (el.children) {
   
            const childrenChecklist = sanatizeUpdatChecklistValueToDb(el.children);
            checklists.push(...childrenChecklist);
        }
        return el;
    });
    return checklists;
};

Here, typescript is throwing

Property ‘children’ does not exist on type ‘TaskBase’

I thought doing this el.children would fix it. but it didn’t