validate

def validate(self, value):
        """validate"""
        # obj can be None or a DataFrame
        if value is None:
            return True
        else:
            try:
                with value.open() as hdulist:
                    self.validate_hdulist(hdulist)
            except Exception:
                _type, exc, tb = sys.exc_info()
                six.reraise(ValidationError, exc, tb)