You have been asked to increase the number of heroes one can see on a single page to 250. (The default is 100). You can do this by:
@admin.register(Hero)
class HeroAdmin(admin.ModelAdmin, ExportCsvMixin):
    ...
    list_per_page = 250
You can also set it to a smaller value. If we set it to 1 as list_per_page = 1 the admin looks like this.
_images/icrease_row_count_to_one.png