Add example argument

Author: IyeOnline

builtins/operators/read_custom_log.cpp

@@ -272,14 +272,14 @@ class read_custom_log_plugin final
     // Using `named_optional`, we add our argument. You can also use the
     // `positional` and/or `named`. See `argument_parser2.hpp`. If you dont need
     // any arguments, you can skip this part.
-    auto time_offset = tenzir::duration{0s};
-    parser.named_optional("time_offset", time_offset);
+    auto time_offset = std::optional<tenzir::duration>{0s};
+    parser.named("time_offset", time_offset);
     // We let the argument_parser parse our arguments. The TRY macro ensures
     // that a parsing failure will stop the setup.
     TRY(parser.parse(inv, ctx));
     // Create the operator instance, passing in any arguments that the operator
     // requires.
-    return std::make_unique<read_custom_log_operator>(time_offset);
+    return std::make_unique<read_custom_log_operator>(*time_offset);
   }
 };