code: def next_available(self, path):
      from nnabla.utils.data_source_loader import get_file_extension
  
      ext = get_file_extension(path)
      if ext not in self.next:
          raise ValueError("Currently, No backend available.")
      else:
          if self.next[ext]:
              self._current_backend = self.next[ext].__class__
              return self.next[ext]
          else:
              raise ValueError("Currently, No backend available.")
  
file_path: nnabla/python/src/nnabla/utils/image_utils/backend_events/image_utils_backend.py
imports: from collections import OrderedDict
label_desc: Use image node_id 7 for calling the ImageUtilsBackend obj's underlying member method code with example usage: obj.next_available(path) and returns: self