code: def list_extensions():
      '''
      List up available extensions.
  
      Note:
          It may not work on some platforms/environments since it depends
          on the directory structure of the namespace packages.
  
      Returns: list of str
          Names of available extensions.
  
      '''
      import nnabla_ext.cpu
      from os.path import dirname, join, realpath
      from os import listdir
      ext_dir = realpath((join(dirname(nnabla_ext.cpu.__file__), '..')))
      return listdir(ext_dirf list_extensions():
      '''
      List up available extensions.
  
      Note:
          It may not work on some platforms/environments since it depends
          on the directory structure of the namespace packages.
  
      Returns: list of str
          Names of available extensions.
  
      '''
      import nnabla_ext.cpu
      from os.path import dirname, join, realpath
      from os import listdir
      ext_dir = realpath((join(dirname(nnabla_ext.cpu.__file__), '..')))
      return listdir(ext_dir)
docs: List up available extensions.
  
      Note:
          It may not work on some platforms/environments since it depends
          on the directory structure of the namespace packages.
  
      Returns: list of str
          Names of available extensions.