          Name of this Vset.
        vfuncs: list or dict
            Dictionary of functions that we want to associate with
        vfunc_keys: list (optional)
            List of names corresponding to each vfunc
        is_async: bool (optional)
            If True, `vfuncs` are computed asynchronously
        output_matching: bool (optional)
            If True, then output keys from this Vset will be matched when used
            in other Vsets
        lazy: bool (optional)
            If True, then vf