@classmethod
    def from_counting_attr(cls, name, ca, type=None):
        # type holds the annotated value. deal with conflicts:
        if type is None:
            type = ca.type
        elif ca.type is not None:
            raise ValueError(
                f"Type annotation and type argument for {name} cannot both be present"
            )
        inst_dict = {
            k: getattr(ca, k)
            for k
            in Attribute.__slots__
            if k not in (
                "name", "validator", "default", "type", "convert",
            )  # exclude methods and deprecated alias
        }
        return cls(
            name=name, validator=ca._validator, default=ca._default, type=type,
            **inst_dict
        )