code: private DataFrame getDataFrameToPersist(String query, String subQuery)
      {
          EntityMetadata entityMetadata = getEntityMetadata();
  
          Client client = entityMetadata != null ? persistenceDelegeator.getClient(entityMetadata)
                  : persistenceDelegeator.getClient(kunderaQuery.getPersistenceUnit());
  
          return ((SparkClient) client).getDataFrame(subQuery, entityMetadata, getKunderaQuery());
      }
docs: Gets the data frame to persist.
  
  @param query
  the query
  @param subQuery
  the sub query
  @return the data frame to persist