public function sumSubtable(DataTable $subTable)
{
if ($this->isSubtableLoaded) {
$thisSubTable = $this->getSubtable();
} else {
$this->warnIfSubtableAlreadyExists();
$thisSubTable = new DataTable();
$this->setSubtable($thisSubTable);
}
$columnOps = $subTable->getMetadata(DataTable::COLUMN_AGGREGATION_OPS_METADATA_NAME);
$thisSubTable->setMetadata(DataTable::COLUMN_AGGREGATION_OPS_METADATA_NAME, $columnOps);
$thisSubTable->addDataTable($subTable);
}