code: def update(self, **kwargs):
          
          kwargs['stack'] = self.stack_mark(inspect.stack())
          kwargs['primary_key'] = self.primary_key
          column_names = self.table_schema().keys()
          now = datetime.utcnow()
          if 'updated_at' in column_names:
              kwargs['values']['updated_at'] = now
          results = self.db_adapter(role='master').update(**kwargs)
          return self.record_or_model(results)
docs: Performs an UPDATE statement on the model's table in the master database.
  
          :param values: A dictionary of values to update. ``datetime``, ``dict`` and ``bool`` objects can be passed as is and will be correctly serialized by psycopg2.
          :type values: dict
          :param where: The WHERE clause. This can be a plain string, a dict or an array.
          :type where: string, dict, array