code: def save(self, commit=True):
          
  
          # walk through the document fields
          for field_name, field in iter_valid_fields(self._meta):
              setattr(self.instance, field_name, self.cleaned_data.get(field_name))
  
          if commit:
              self.instance.save()
  
          return self.instance
docs: save the instance or create a new one..