code: def is_valid_mac_oui(mac_block):
          
          if len(mac_block) != 8:
              return 0
          if ':' in mac_block:
              if len(mac_block.split(':')) != 3:
                  return 0
          elif '-' in mac_block:
              if len(mac_block.split('-')) != 3:
                  return 0
          return 1
docs: checks whether mac block is in format of
          00-11-22 or 00:11:22.
          :return: int