You have been asked to allow csv imports on the Hero admin. You will do this by adding a link to the Hero changelist page, which will take to a page with an upload form. You will write a handler for the POST action to create the objects from the csv.:
class CsvImportForm(forms.Form):
    csv_file = forms.FileField()

@admin.register(Hero)
class HeroAdmin(admin.ModelAdmin, ExportCsvMixin):
    ...
    change_list_template = "entities/heroes_changelist.html"

    def get_urls(self):
        urls = super().get_urls()
        my_urls = [
            ...
            path('import-csv/', self.import_csv),
        ]
        return my_urls + urls

    def import_csv(self, request):
        if request.method == "POST":
            csv_file = request.FILES["csv_file"]
            reader = csv.reader(csv_file)
            # Create Hero objects from passed in data
            # ...
            self.message_user(request, "Your csv file has been imported")
            return redirect("..")
        form = CsvImportForm()
        payload = {"form": form}
        return render(
            request, "admin/csv_form.html", payload
        )
Then you create the entities/heroes_changelist.html template, by overriding the admin/change_list.html template like this.:
{% extends 'admin/change_list.html' %}

{% block object-tools %}
    <a href="import-csv/">Import CSV</a>
    <br />
    {{ block.super }}
{% endblock %}
Finally you create the csv_form.html like this.:
{% extends 'admin/base.html' %}

{% block content %}
    <div>
        <form action="." method="POST" enctype="multipart/form-data">
            {{ form.as_p }}
            {% csrf_token %}

                <button type="submit">Upload CSV</button>
        </form>
    </div>
    <br />

{% endblock %}
With these changes, you get a link on the Hero changelist page.
_images/import_1.png
And the import form apge looks like this.
_images/import_2.png