code: def is_network_source_fw(cls, nwk, nwk_name):
          
          if nwk is not None:
              if nwk.source == fw_const.FW_CONST:
                  return True
              return False
          if nwk_name in fw_const.DUMMY_SERVICE_NWK and (
             len(nwk_name) == len(fw_const.DUMMY_SERVICE_NWK) +
             fw_const.SERVICE_NAME_EXTRA_LEN):
              return True
          if nwk_name in fw_const.IN_SERVICE_NWK and (
             len(nwk_name) == len(fw_const.IN_SERVICE_NWK) +
             fw_const.SERVICE_NAME_EXTRA_LEN):
              return True
          if nwk_name in fw_const.OUT_SERVICE_NWK and (
             len(nwk_name) == len(fw_const.OUT_SERVICE_NWK) +
             fw_const.SERVICE_NAME_EXTRA_LEN):
              return True
          return False
docs: Check if SOURCE is FIREWALL, if yes return TRUE.
  
          If source is None or entry not in NWK DB, check from Name.
          Name should have constant AND length should match.