docs: public GenericData set(String fieldName, Object value) {
      FieldInfo fieldInfo = classInfo.getFieldInfo(fieldName);
      if (fieldInfo != null) {
        fieldInfo.setValue(this, value);
      } else {
        if (classInfo.getIgnoreCase()) {
          fieldName = fieldName.toLowerCase(Locale.US);
        }
        unknownFields.put(fieldName, value);
      }
      return this;
    }