Django admin : Expand all the entries in stackedinline by default

In my django application, I am using an admin interface to see all the products and each product can have several images. I have stacked the images into the Product Page using the below code

class ProductImage_Inline(admin.StackedInline):
    model = ProductImage
    extra = 3

    formfield_overrides = {
        ImageWithThumbnailField : {'widget' : AdminImageWithThumbnailWidget},

By default, in the Product Admin page I can't see all the images because all the entires in the StackedInline are collapsed by default. I have to manually click on each of them to expand so as to see the image.

How can I expand all the entries in a StackedInline by default?

P.S : I am using Grappelli theme and suspect that it is collapsing them by default