Issue: code generate for nested group broken

pbdata.proto

syntax = "proto2";
package pbdata;
message ValueType {
	optional int32 int_type =1;
	optional int64 long_type = 2;
	optional float float_type = 3;
	optional string string_type =4;
}
message Log {
	required int64 log_timestamp =1;
	optional string ip = 2;
	optional group Field  = 3 {
		repeated group Map = 1 {
			required string key = 1;
			optional ValueType value = 2;
		}
	}
}