Returns a merged dictionary of all step cleaned_data dictionaries.
        If a step contains a `FormSet`, the key will be prefixed with formset
        and contain a list of the formset' cleaned_data dictionaries.

def get_all_cleaned_data(self):
        """
        Returns a merged dictionary of all step cleaned_data dictionaries.
        If a step contains a `FormSet`, the key will be prefixed with formset
        and contain a list of the formset' cleaned_data dictionaries.
        """
        cleaned_data = {}
        for form_key in self.get_form_list():
            form_obj = self.get_form(
                step=form_key,
                data=self.storage.get_step_data(form_key),
                files=self.storage.get_step_files(form_key)
            )
            if form_obj.is_valid():
                if isinstance(form_obj.cleaned_data, (tuple, list)):
                    cleaned_data.update({
                        'formset-%s' % form_key: form_obj.cleaned_data
                    })
                else:
                    cleaned_data.update(form_obj.cleaned_data)
        return cleaned_data