src/Repository/Doctrine/Repository.php
public function listKeysAndValues($key, $value, QueryParameters $queryParameters = null) {
        $results = $this->columns([$key, $value], $queryParameters);

        $return = [];
        foreach($results as $result) {
            $return[$result[$key]] = $result[$value];
        }

        return $return;
    }
public function listKeysAndValues($key, $value, QueryParameters $queryParameters = null) {
        $results = $this->columns([$key, $value], $queryParameters);

        $return = [];
        foreach($results as $result) {
            $return[$result[$key]] = $result[$value];
        }

        return $return;
    }
Lists columns of the entity like this:
1 => Title
3 => Foo
4 => Yoyo

@param $key
@param $value
@param QueryParameters $queryParameters
@return array