code: def CreateFile(filename):
    
    with gcs.open(filename, 'w') as f:
      f.write('abcde\n')
  
    blobstore_filename = '/gs' + filename
    return blobstore.create_gs_key(blobstore_filename)
docs: Create a GCS file with GCS client lib.
  
    Args:
      filename: GCS filename.
  
    Returns:
      The corresponding string blobkey for this GCS file.