code: def get_db_prep_save(self, value, connection, **kwargs):
          
          if value is None and self.null:
              return None
          # default values come in as strings; only non-strings should be
          # run through `dumps`
          if not isinstance(value, six.string_types):
              value = dumps(value)
  
          return value
docs: Convert our JSON object to a string before we save