docs: def compareImage(self, body, plotShape="circle", imageScalar=2, imageEncoding="base64/png"):
          """Get an overlay image for two expressions
          Args:
              body, ExpressionOperation: The JSON encoded comparison array to be evaluated (required)
              plotShape, str: The image shape (optional)
              imageScalar, int: The scale of the image (optional)
              imageEncoding, str: The encoding of the returned image (optional)
          Returns:
              str with the raw byte data of the image
          Raises:
              CorticalioException: if the request was not successful
          """
          return self._image.getOverlayImage(self._retina, body, plotShape, imageScalar, imageEncoding)