/**
  * Calculates the NPath complexity for the given callable instance.
  *
  * @param \PDepend\Source\AST\AbstractASTCallable $callable
  * @return string
  * @since 0.9.12
  */
 private function _calculateNPathComplexity(AbstractASTCallable $callable)
 {
     $analyzer = $this->_createAnalyzer();
     $callable->accept($analyzer);
     $metrics = $analyzer->getNodeMetrics($callable);
     return $metrics['npath'];
 }