def process_image(self, image, image_format, **kwargs):
raise NotImplementedError(<EOL>'<STR_LIT>'<EOL>)<EOL>
Ensure NotImplemented is raised if not overloaded by subclasses.

Arguments:
    * `image`: a PIL Image instance
    * `image_format`: str, a valid PIL format (i.e. 'JPEG' or 'GIF')

Returns a BytesIO representation of the resized image.

Subclasses MUST implement this method.