What does the input_mask look like?

[Gasoonjia]

Hi Vivan!
I want to remove something from my image through your code, and according to your READ.MD file and your code, I should provide a input_mask file to let the algorithm know which part should be removed.
But I'm not sure about the format of the input_mask file, can you tell me more information about it?
Thank you sooooo much!!!

[tomo-dev-2018]

The sample file and the corresponding mask look like this:
Sample picture:

Sample mask:

The key issue is to sorround the object(mask) with 'total' black ;) - I did it with the help of GIMP