code: protected function computeLevel() {
      list($node, $nesting) = $this->determineDepth($this);
  
      if ( $node->equals($this) )
        return $this->ancestors()->count();
  
      return $node->getLevel() + $nesting;
    }
docs: Compute current node level. If could not move past ourseleves return
  our ancestor count, otherwhise get the first parent level + the computed
  nesting.
  
  @return integer