code: def form_upload_valid(self, form):
          
          self.current_step = self.STEP_LINES
  
          lines = form.cleaned_data['file']
          initial_lines = [dict(zip(self.get_columns(), line)) for line in lines]
          inner_form = self.get_form(self.get_form_class(),
              data=None,
              files=None,
              initial=initial_lines,
          )
          return self.render_to_response(self.get_context_data(form=inner_form))
docs: Handle a valid upload form.