code: private static Object tupleFieldToSingleField(FieldDescriptor fieldDescriptor, Object tupleField) {
      // type convertion should match with ProtobufToPig.getPigScriptDataType
      switch (fieldDescriptor.getType()) {
      case ENUM:
        return toEnumValueDescriptor(fieldDescriptor, (String) tupleField);
      case BOOL:
        return Boolean.valueOf((Integer)tupleField != 0);
      case BYTES:
        return ByteString.copyFrom(((DataByteArray)tupleField).get());
      default:
        return tupleField;
      }
    }
docs: Converts a tupleField string to its corresponding protobuf enum type if necessary, otherwise
  returns the tupleField as is.
  @param fieldDescriptor the FieldDescriptor for the given tuple field
  @param tupleField the tupleField being converted to a protobuf field
  @return the protobuf type for the given tupleField. This will be the tupleField itself unless it's an enum, in which case this will return the enum type for the field.