indicate that the logging key expects a string data type

The example JSON has a boolean datatype for the logging key. If you use this JSON, the comparison will fail in MDLConfig.m:52 because it is expecting a string datatype.

Another solution could be to allow boolean and string data types for the logging key.

I have indicated with a comment that the value must be a string for this key. Technically this is invalid JSON. Not sure of a better way to make it obvious enough if a string is expected.