code: def _validate_importers(importers):
      
      # They could have no importers, that's chill
      if importers is None:
          return None
  
      def _to_importer(priority, func):
          assert isinstance(priority, int), priority
          assert callable(func), func
          return (priority, _importer_callback_wrapper(func))
  
      # Our code assumes tuple of tuples
      return tuple(_to_importer(priority, func) for priority, func in importers)
docs: Validates the importers and decorates the callables with our output
      formatter.