docs: def db_set(table, record, column, value, if_exists=False):
      '''
      Sets a column's value for a specific record.
  
      Args:
          table: A string - name of the database table.
          record: A string - identifier of the record.
          column: A string - name of the column.
          value: A string - the value to be set
          if_exists: A boolean - if True, it is not an error if the record does
              not exist.
  
      Returns:
          None on success and an error message on failure.
  
      CLI Example:
      .. code-block:: bash
  
         salt '*' openvswitch.db_set Interface br0 mac 02:03:04:05:06:07
      '''
      cmd = ['ovs-vsctl']
      if if_exists:
          cmd += ['--if-exists']
      cmd += ['set', table, record, '{0}={1}'.format(column, json.dumps(value))]
      result = __salt__['cmd.run_all'](cmd)
      if result['retcode'] != 0:
          return result['stderr']
      else:
          return None