src/Eloquent/AbstractAdapter.php
public function queryToOne($relation, EncodingParametersInterface $parameters)
    {
        return $this->queryOne(
            $relation->newQuery(),
            $this->getQueryParameters($parameters)
        );
    }
public function queryToOne($relation, EncodingParametersInterface $parameters)
    {
        return $this->queryOne(
            $relation->newQuery(),
            $this->getQueryParameters($parameters)
        );
    }
Query the resource when it appears in a to-one relation of a parent resource.

For example, a request to `/posts/1/author` will invoke this method on the
user adapter when the author relation returns a `users` resource.

@param Relations\BelongsTo|Relations\HasOne|Builder $relation
@param EncodingParametersInterface $parameters
@return mixed