Flask-WTF: passing object to Ninja2-template => no filter named ‘tojason’

From one of my Flask routes I pass an object (selectedStek) to a Jinja2 template

from flask import (Blueprint, current_app, flash, jsonify, redirect, render_template, request, url_for)
from flask_login import current_user, login_required
from flask_uploads import IMAGES, UploadSet, configure_uploads

from . import db
from .forms import createStekForm
from .models import Stek, Stektype

stekken = Blueprint("stekken", __name__)


@stekken.route("/stek_modify/<stekId>", methods=['GET', 'POST'])
@login_required

def stek_modify(stekId):

    form = createStekForm()
    selectedStek = Stek.query.filter_by(id = int(stekId)).first() 

    return render_template('stek_modify.html', form=form, stek=selectedStek"])

Which I then want to use in a javascript with tojason

{% block content %}

<h3>{{stek.place}} </h3>

{% endblock %}


{% block scripts %}

<script>

    $(document).ready(function () {

    console.log( "ready!" );

    varKo = ({{stek.place|tojson }});

    console.log(varKo);
    
    }); // document.readyFunction

</script>
    
{% endblock %}

This code returns an error “jinja2.exceptions.TemplateAssertionError: No filter named ‘tojason'”.

I just can’t figure out what’s wrong.
Probably something simple but I need some help to figure it out