code: protected function getRelationshipPaths($includePaths)
      {
          return $this
              ->convertIncludePaths($includePaths)
              ->merge($this->defaultWith)
              ->unique()
              ->all();
      }
docs: Get the relationship paths to eager load.
  
  @param Collection|array $includePaths
  the JSON API resource paths to be included.
  @return array