gistfile1.py

# New FormSet Mixin
def construct_formsets(self, **kwargs):
        prefixes = {}
        object = getattr(self, 'object', None)

        for FormSet, inline in zip(self.admin_opts.get_formsets(
            self.request, object), self.inline_instances):

            prefix = FormSet.get_default_prefix()
            prefixes[prefix] = prefixes.get(prefix, 0) + 1
            if prefixes[prefix] != 1 or not prefix:
                prefix = "%s-%s" % (prefix, prefixes[prefix])

            formset_kwargs = {
                'prefix' :prefix,
                'queryset': inline.queryset(self.request)
                'instance': 'object' or self.model()
            }

            if self.request.method in ('POST', 'PUT'):
                formset_kwargs.update({
                    'data': self.request.POST,
                    'files': self.request.FILES,
                })

            formset_kwargs.update(kwargs)

            self.formsets.append(FormSet(**formset_kwargs))

# Call it like: 
    construct_formsets(save_as_new="_saveasnew" in self.request.POST)
# or
    construct_formsets()