Adding another enum and field usage just to see what it looks like

protobuf/src/tutorial/addressbook.proto

@@ -1,9 +1,17 @@
 package tutorial;
 
+enum Gender {
+    NONE = 0;
+    MALE = 1;
+    FEMALE = 2;
+    OTHER = 3;
+}
+
 message Person {
     required string name = 1;
     required int32 id = 2;
     optional string email = 3;
+    optional Gender type = 4 [default = NONE];
 
     enum PhoneType {
         MOBILE = 0;
@@ -16,7 +24,7 @@ message Person {
         optional PhoneType type = 2 [default = HOME];
     }
 
-    repeated PhoneNumber phone = 4;
+    repeated PhoneNumber phone = 5;
 }
 
 message AddressBook {