Here's a first cut at a patch.  All signatures now start with "sig=(".

I also added a special marker: if the first parameter starts with "$", we know for certain it's a "self" (or "module" or "type") parameter.  This means we can lose the heuristics for "do we have a self parameter?", making inspect.Signature a little more bullet-proof.  "$" was chosen as it isn't a legal token in Python.