@Override
    public void writeTo(com.google.protobuf.CodedOutputStream output)
                        throws java.io.IOException {
      if (((bitField0_ & 0x00000001) != 0)) {
        com.google.protobuf.GeneratedMessageV3.writeString(output, 1, name_);
      }
      if (((bitField0_ & 0x00000002) != 0)) {
        output.writeInt32(2, id_);
      }
      if (((bitField0_ & 0x00000004) != 0)) {
        com.google.protobuf.GeneratedMessageV3.writeString(output, 3, email_);
      }
      getUnknownFields().writeTo(output);
    }
<code>optional string email = 3;</code>
@return The bytes for email.
core/src/test/java/com/alibaba/fastjson2/protobuf/PersonOuterClass.java