Method _value_validate

tests/test_traitlets.py:1968–1974

(self, proposal)

            @validate("value")
            def _value_validate(self, proposal):
                value = proposal["value"]
                if self.parity == "even" and value % 2:
                    raise TraitError("Expected an even number")
                if self.parity == "odd" and (value % 2 == 0):
                    raise TraitError("Expected an odd number")
                return value

        u = Parity()
        u.parity = "odd"