Classes in __main__ modules will not work as arguments.

[dan-blanchard]

I'm not sure if this is a bug or just a limitation at this point, but if you have an executable script that defines a class in it, and then you try to pass an object of that type to grid_map, you will run into a pickling error, because it can't find the __main__ module when it tries to unpickle it.

[dan-blanchard]

I'm more convinced this is just simply a limitation of pickling at this point, so I'm no longer marking it a bug.