code: private VarSymbol getDefinedSerializableFields(ClassSymbol def) {
          Names names = def.name.table.names;
  
          /* SERIALIZABLE_FIELDS can be private,
           * so must lookup by ClassSymbol, not by ClassDocImpl.
           */
          for (Scope.Entry e = def.members().lookup(names.fromString(SERIALIZABLE_FIELDS)); e.scope != null; e = e.next()) {
              if (e.sym.kind == Kinds.VAR) {
                  VarSymbol f = (VarSymbol)e.sym;
                  if ((f.flags() & Flags.STATIC) != 0 &&
                      (f.flags() & Flags.PRIVATE) != 0) {
                      return f;
                  }
              }
          }
          return null;
      }
docs: /*
  Check for explicit Serializable fields.
  Check for a private static array of ObjectStreamField with
  name SERIALIZABLE_FIELDS.