flatten a dict baseline (should remove class method)

flatten.py

def flatten(cls, obj):
        if isinstance(obj, (str, int, float)):
            return obj
        elif isinstance(obj, list):
            return [cls.flatten(item) for item in obj]
        elif isinstance(obj, dict):
            flatobj = {}
            for key, val in obj.items():
                if isinstance(val, list):
                    for i, item in enumerate(val):
                        if not isinstance(item, dict):
                            flatobj[key + '.i' + str(i)] = cls.flatten(item)
                        else:
                            for subkey, subval in cls.flatten(item).items():
                                flatobj[key + '.i' + str(i) + '.' + subkey] = subval
                elif not isinstance(val, dict):
                    flatobj[key] = cls.flatten(val)
                else:
                    for subkey, subval in cls.flatten(val).items():
                        flatobj[key + '.' + subkey] = subval
            return flatobj