When you use code generation, this declaration is automatically created in the deployment.h file.
There is an example of a such enum declaration:
   typedef enum
   {
     node1_partition_secret_outgoing = 0,
     node1_partition_topsecret_outgoing = 1,
     node1_partition_unclassified_outgoing = 2,
     invalid_local_port = 3
   } pok_port_local_identifier_t;