code: public function scopeLimitDepth($query, $limit) {
      $depth  = $this->exists ? $this->getDepth() : $this->getLevel();
      $max    = $depth + $limit;
      $scopes = array($depth, $max);
  
      return $query->whereBetween($this->getDepthColumnName(), array(min($scopes), max($scopes)));
    }
docs: Provides a depth level limit for the query.
  
  @param   query   \Illuminate\Database\Query\Builder
  @param   limit   integer
  @return  \Illuminate\Database\Query\Builder