def __call__(self, inst, attr, value):
        """
        We use a callable class to be able to change the ``__repr__``.
        """
        if not self.interface.providedBy(value):
            raise TypeError(
                "'{name}' must provide {interface!r} which {value!r} "
                "doesn't.".format(
                    name=attr.name, interface=self.interface, value=value
                ),
                attr,
                self.interface,
                value,
            )

        We use a callable class to be able to change the ``__repr__``.
        
product/gradle-plugin/src/main/python/attr/validators.py