'Adds mapping of `new_key` to `key_to_response` to make it possible to
associate many keys with single response
:param new_key: new key (e.g. url from redirect)
:param key_to_response: key which can be found in :attr:`responses`
:return:'

def add_key_mapping(self, new_key, key_to_response):

    self.keys_map[new_key] = key_to_response
