src/Resources/ResourceFactory.php
protected function resolveResourceKey($data, string $resourceKey = null)
    {
        return isset($resourceKey) ? $resourceKey : $this->resourceKeyResolver->resolve($data);
    }
protected function resolveResourceKey($data, string $resourceKey = null)
    {
        return isset($resourceKey) ? $resourceKey : $this->resourceKeyResolver->resolve($data);
    }
Resolve a resource key.

@param  mixed       $data
@param  string|null $resourceKey
@return null|string