Django Admin - add collapse to a fieldset, but have it start expanded

Accoding with the grappelli docs only need to add "classes" : ('grp-collapse grp-closed')

for example

class EntryOptions(admin.ModelAdmin):
   ...
   fieldsets = (
     ('', {
        'fields': ('title', 'subtitle', 'slug', 'pub_date', 'status',),
     }),
     ('Flags', {
        'classes': ('grp-collapse grp-closed',),
        'fields' : ('flag_front', 'flag_sticky', 'flag_allow_comments',),
    }),

note: if you use grappelli version < 2.4 use 'grp-closed' instead 'collapse-closed'* actually 'collapse-close' still is working but is recommended to use the new classes

admin.py:

class PageAdmin(admin.ModelAdmin):
    fieldsets = (
        (None, {
            'fields': ('title', 'content', )
        }),
        ('Other Informations', {
            'classes': ('collapse', 'open'),
            'fields': ('slug', 'create-date',)
        }),
    )

templates/app_label/model_name/change_form.html:

{% extends "admin/model_name/change_form.html" %}

{% block extrahead %}
    {{ block.super }}
    <script src="{{ STATIC_URL }}admin/js/collapse-open.js" type="text/javascript"></script>
{% endblock %}

static/admin/js/collapse-open.js:

(function($) {
    $(document).ready(function() {
        $('fieldset.collapse.open').removeClass('collapsed');
    });
})(django.jQuery);

I know this is real old but I also just came across this issue. After thinking about it way too hard I found an easy solution which seems to get the job done involving 0 plugins or additional js.

Within fieldsets construct Add 'collapse in' rather than 'collapse' to class:

fieldsets = [
    ('Start Expanded', {
    'fields': ['field1', 'field2', 'field3'], 
    'classes': ['collapse in',]
    })
]

django-grappelli provides this as one of the features. Here's the wiki page about that feature (with screenshots).