code: public boolean isSet(_Fields field) {
      if (field == null) {
        throw new IllegalArgumentException();
      }
  
      switch (field) {
      case SESSION_HANDLE:
        return isSetSessionHandle();
      case CATALOG_NAME:
        return isSetCatalogName();
      case SCHEMA_NAME:
        return isSetSchemaName();
      case FUNCTION_NAME:
        return isSetFunctionName();
      }
      throw new IllegalStateException();
    }
docs: Returns true if field corresponding to fieldID is set (has been assigned a value) and false otherwise