def _handle_variant_overrides(self, environ):
        # Parse the QUERY_STRING into a dictionary, and make an editable copy
        parsed = dict(parse_qsl(environ.get('QUERY_STRING', '')))
        qs = parsed.copy()

        # For each key that starts with cleaver: ...
        for k in parsed:
            if k.startswith('cleaver:'):
                # Store the key -> value in ``environ['cleaver.override']``
                # and remove it from the editable ``qs`` copy.
                environ.setdefault('cleaver.override', {})[
                    k.split('cleaver:')[1]
                ] = qs.pop(k)

        # If any overriden variables were changed, re-encode QUERY_STRING so
        # that the next WSGI layer doesn't see the parsed ``cleaver:``
        # arguments.
        if environ in 'cleaver.override':
            environ['QUERY_STRING'] = urlencode(qs)
dataset/ETHPy150Open ryanpetrello/cleaver/cleaver/middleware.py/SplitMiddleware._handle_variant_overrides/swapped operands of `in`