code: private static void convertSelectPartHelper(
        Builder<SoyMsgPart> newMsgPartsBuilder,
        StringBuilder currRawTextSb,
        SoyMsgSelectPart origSelectPart) {
  
      currRawTextSb.append(getSelectOpenString(origSelectPart.getSelectVarName()));
  
      for (Case<String> selectCase : origSelectPart.getCases()) {
        currRawTextSb.append(getSelectCaseOpenString(selectCase.spec()));
        convertMsgPartsHelper(
            newMsgPartsBuilder, currRawTextSb, selectCase.parts(), /* isInPlrselPart= */ true);
        currRawTextSb.append(getSelectCaseCloseString());
      }
  
      currRawTextSb.append(getSelectCloseString());
    }
docs: Private helper for {@code convertMsgPartsToEmbeddedIcuSyntax()} to convert a select part.
  
  @param newMsgPartsBuilder The new msg parts being built.
  @param currRawTextSb The collector for the current raw text, which hasn't yet been turned into
  a SoyMsgRawTextPart and added to newMsgPartsBuilder because it might not be complete.
  @param origSelectPart The select part to convert.