Adding class to images and videos with Summernote widget in Django 2 - css

Question

I'm looking for a way to add a class, which I could modify in css, to images and videos in both editor forms and html templates displaying the form. I'm using the SummernoteInplaceWidget() from django-summernote package and it's working fine except this feature.
I use bootstrap 4 with it.
Any ideas?
Thanks in advance.
forms.py:
from django.forms import ModelForm
from django_summernote.widgets import SummernoteInplaceWidget
from .models import Post
class PostFormModel(ModelForm):
class Meta:
model = Post
fields = ['title', 'content', 'image', ]
widgets = {
'content': SummernoteInplaceWidget(attrs={'class': 'summer-img-class'}),
}
post_form.html:
{% extends "blog/base.html" %}
{% load crispy_forms_tags %}
{% block mt %} mt-2 {% endblock mt %}
{% block content %}
<div class="content-section">
<form method="POST" enctype="multipart/form-data">
{% csrf_token %}
<fieldset class="form-group">
<legend class="border-bottom mb-4">Blog Post</legend>
{{ form|crispy }}
{% if form.image.errors %}
<div class="alert alert-danger">
{{ form.image.errors }}
</div>
{% endif %}
</fieldset>
<div class="form-group">
<button class="btn btn-outline-info" type="submit">Post</button>
</div>
</form>
{% block jquery %}
{{ form.media }}
{% endblock %}
</div>
{% endblock content %}
post_detail.html:
{% extends "blog/base.html" %}
{% block mt %} mt-2 {% endblock mt %}
{% block content %}
<article class="media content-section">
<div class="shadow-sm rounded row media-body">
<div class="col-md-3 col-sm-3 col-3 align-self-center">
<img class="rounded-circle article-img align-middle mx-auto d-none d-sm-block " src="{{ object.author.profile.image.url }}">
<img class="rounded-circle article-img-sm align-midle mx-auto d-block d-sm-none " src="{{ object.author.profile.image.url }}"">
</div>
<div class="col-md-9 col-sm-9 col-9">
<div class="article-metadata">
<a class="mr-2" href="{% url 'user-posts' post.author.username %}">{{ post.author }}</a>
<small class="text-muted">{{ object.date_posted|date:"F d, Y" }}</small>
{% if object.author == user %}
<div>
<a class="btn btn-secondary btn-sm mt-1 mb-1" href="{% url 'post-update' object.id %}">Update</a>
<a class="btn btn-danger btn-sm mt-1 mb-1" href="{% url 'post-delete' object.id %}">Delete</a>
</div>
{% endif %}
</div>
<h2><a class="article-title" href="{% url 'post-detail' post.id %}">{{ object.title }}</a></h2>
</div>
<div class="row media-body pt-3">
<div class="col-md-12">
{% if post.image %}
<img alt="" src="{{ object.image.large.url }}" class="post_image rounded mx-auto mb-2 d-block"/>
{% endif %}
<p class="article-content ml-3">{{ object.content|safe }}</p>
</div>
</div>
</div>
</article>
{% endblock content %}
I tried to add some styling to .article-content, it didn't have any effect, the same for this class in css (I imagine it can be more effectively):
.summer-img-class * {
max-width: 100%;
max-height: 400px;
object-fit: cover;
margin: auto;
}
Maybe it should be done with Jquery somehow, I don't know.