src/Eloquent/Concerns/QueriesRelations.php
protected function adapterFor($relation)
    {
        $adapter = $this->getStore()->adapterFor($relation->getModel());

        if (!$adapter instanceof AbstractAdapter) {
            throw new RuntimeException('Expecting inverse resource adapter to be an Eloquent adapter.');
        }

        return $adapter;
    }
protected function adapterFor($relation)
    {
        $adapter = $this->getStore()->adapterFor($relation->getModel());

        if (!$adapter instanceof AbstractAdapter) {
            throw new RuntimeException('Expecting inverse resource adapter to be an Eloquent adapter.');
        }

        return $adapter;
    }
Get an Eloquent adapter for the supplied record's relationship.

@param Relation|Builder $relation
@return AbstractAdapter