code: public function isShared($abstract)
      {
          if (!isset($this->bindings[$abstract])) {
              throw Internal\Exception\ReflectionExceptionFactory::invalidArgument(
                  sprintf("Parameter 1 of %s must be valid keys in binding container stack.", __METHOD__)
              );
          }
  
          return ($this->bindings[$abstract]['shared'] ? true : false);
      }
docs: Determine if a given type is shared.
  
  @param string $abstract
  @return bool