how does encoding of custom fieldoptions work

[LakshmiKanth Gupta]

syntax="proto3";

import "google/protobuf/descriptor.proto"

extend google.protobuf.FieldOptions{

   bool presence=50001;

}

message Mymessage

{

    int32 foo=1[(presence)=true];

    string bar=2;

}

I wrote following code and encoded:

Mymessage l_message;

l_message.set_foo(1);

l_message.set_bar("hello");

When I encoded it using l_message.SerializeToString(), the encoded payload doesn't have field options. Am I missing something? Please help.

What will be payload with custom field options encoded?