original_string: public function isSingleton(string $abstract) : bool
      {
          if (! $this->has($abstract)) {
              throw new NotFoundException("Element '$abstract' not found");
          }
  
          return $this->collection[$abstract] instanceof Closure === false;
      }
code: public function isSingleton(string $abstract) : bool
      {
          if (! $this->has($abstract)) {
              throw new NotFoundException("Element '$abstract' not found");
          }
  
          return $this->collection[$abstract] instanceof Closure === false;
      }
code_tokens: public function isSingleton ( string $ abstract ) : bool { if ( ! $ this -> has ( $ abstract ) ) { throw new NotFoundException ( "Element '$abstract' not found" ) ; } return $ this -> collection [ $ abstract ] instanceof Closure === false ; }
docstring: Verify if an element has a singleton instance.
  
  @param  string The class name or container element name to resolve dependencies.
  
  @throws NotFoundException When $abstract does not exists
  @return bool
docstring_tokens: Verify if an element has a singleton instance .