code: def _image_url(array, fmt='png', mode="data", quality=90, domain=None):
    
    supported_modes = ("data")
    if mode not in supported_modes:
      message = "Unsupported mode '%s', should be one of '%s'."
      raise ValueError(message, mode, supported_modes)
  
    image_data = serialize_array(array, fmt=fmt, quality=quality)
    base64_byte_string = base64.b64encode(image_data).decode('ascii')
    return "data:image/" + fmt.upper() + ";base64," + base64_byte_string
docs: Create a data URL representing an image from a PIL.Image.
  
    Args:
      image: a numpy
      mode: presently only supports "data" for data URL
  
    Returns:
      URL representing image