/**
* {@inheritdoc}
*/
public function getFieldLabels($groupable_only = FALSE
) { $options =
[];
foreach ($this->
getHandlers('relationship'
) as $relationship =>
$handler) { $relationships[$relationship] =
$handler->
adminLabel();
} foreach ($this->
getHandlers('field'
) as $id =>
$handler) { if ($groupable_only && !
$handler->
useStringGroupBy()) { // Continue to next handler if it's not groupable.
continue;
} if ($label =
$handler->
label()) { $options[$id] =
$label;
} else { $options[$id] =
$handler->
adminLabel();
} if (!
empty($handler->options
['relationship'
]) && !
empty($relationships[$handler->options
['relationship'
]])) { $options[$id] = '(' .
$relationships[$handler->options
['relationship'
]] . ') ' .
$options[$id];
}