def accessor(self):
        """Get an attribute's accessor with the getter and the setter.

        :return: `Accessor` instance.
        """
        if isinstance(self.attr, Accessor):
            return self.attr

        if callable(self.attr):
            return Accessor(getter=self.attr)

        attr = self.attr or self.name
        return Accessor(getter=attr, setter=attr)
Get an attribute's accessor with the getter and the setter.

        :return: `Accessor` instance.