environment/lib/python2.7/site-packages/IPython/utils/traitlets.py
def validate(self, obj, value):
        """Validates that the value is a valid object instance."""
        try:
            if issubclass(value, self.klass):
                return value
        except:
            if (value is None) and (self._allow_none):
                return value

        self.error(obj, value)
def validate(self, obj, value):
        """Validates that the value is a valid object instance."""
        try:
            if issubclass(value, self.klass):
                return value
        except:
            if (value is None) and (self._allow_none):
                return value

        self.error(obj, value)
Validates that the value is a valid object instance.