'Build the configuration for this new/saved visualization by combining
any existing config and the kwargs (gen. from the url query).'

def _build_config(self, config, trans=None, **kwargs):

    if config:
        config = copy.copy(config)
    else:
        config = {}
    config_from_kwargs = self._kwargs_to_config(trans, kwargs)
    config.update(config_from_kwargs)
    config = utils.OpenObject(**config)
    return config
