code: def _fsync_files(filenames):
      
      touched_directories = set()
  
      mode = os.O_RDONLY
  
      # Windows
      if hasattr(os, 'O_BINARY'):
          mode |= os.O_BINARY
  
      for filename in filenames:
          fd = os.open(filename, mode)
          os.fsync(fd)
          os.close(fd)
          touched_directories.add(os.path.dirname(filename))
  
      # Some OSes also require us to fsync the directory where we've
      # created files or subdirectories.
      if hasattr(os, 'O_DIRECTORY'):
          for dirname in touched_directories:
              fd = os.open(dirname, os.O_RDONLY | os.O_DIRECTORY)
              os.fsync(fd)
              os.close(fd)
docs: Call fsync() a list of file names
  
      The filenames should be absolute paths already.