message Serializer {
  optional bool bool_field         = 1;
  optional bytes bytes_field       = 2;
  optional double double_field     = 3;
  optional fixed32 fixed32_field   = 4;
  optional fixed64 fixed64_field   = 5;
  optional float float_field       = 6;
  optional int32 int32_field       = 7;
  optional int64 int64_field       = 8;
  optional sfixed32 sfixed32_field = 9;
  optional sfixed64 sfixed64_field = 10;
  optional sint32 sint32_field     = 11;
  optional sint64 sint64_field     = 12;
  optional string string_field     = 13;
  optional uint32 uint32_field     = 14;
  optional uint64 uint64_field     = 15;
}