def build(cfg, registry, key='name'):
    """Build a module from config dict.
    Args:
        cfg (dict): Config dict. It should at least contain the key.
        registry (XXX): The registry to search the type from.
        key (str): the key.
    Returns:
        obj: The constructed object.
    """

    assert isinstance(cfg, dict) and key in cfg

    cfg_copy = cfg.copy()
    obj_type = cfg_copy.pop(key)

    obj_cls = registry.get(obj_type)
    if obj_cls is None:
        raise KeyError('{} is not in the {} registry'.format(
                obj_type, registry.name))
    return obj_cls(**cfg_copy)