docs: def db_get(table, record, column, if_exists=False):
      '''
      Gets 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.
          if_exists: A boolean - if True, it is not an error if the record does
              not exist.
  
      Returns:
          The column's value.
  
      CLI Example:
      .. code-block:: bash
  
         salt '*' openvswitch.db_get Port br0 vlan_mode
      '''
      cmd = ['ovs-vsctl', '--format=json', '--columns={0}'.format(column)]
      if if_exists:
          cmd += ['--if-exists']
      cmd += ['list', table, record]
      result = __salt__['cmd.run_all'](cmd)
      if result['retcode'] != 0:
          raise CommandExecutionError(result['stderr'])
      output = _stdout_parse_json(result['stdout'])
      if output['data'] and output['data'][0]:
          return output['data'][0][0]
      else:
          return None