Strange json formatting in png metadata

[Hangover3832]

When in unpack the metadata from a png with the following code:

from PIL import Image
im = Image.open(filename)
print(str(im.info))

the putput looks like

{'prompt': '{
        "10": {
        ....
        }
    }', 'workflow': '{
        "last_node_id": 550,
        "last_link_id": 1372,
        ............
    }
}'
}

which does not look like a valid json, the keys should be in double quotes, the 'prompt' and 'workflow' sub-jsons are in quotes (where they shouldn't).
A valid json should look like this:

{
"prompt": {
    "10": {
    ....
    }
},
"workflow": {
    "last_node_id": 550,
    "last_link_id": 1372,
    ............
}
}

I mean, things work fine so far, I'm not sure if this is (or could lead to) an issue at some point.