Other is more specific than self.   Other is bounded within self.

def is_entailed_by(self, other):
        """
        Other is more specific than self.   Other is bounded within self.
        """
        other = self.coerce(other)
        to_i = self.to_i
        return to_i(other.low) >= to_i(self.low) and \
                to_i(other.high) <= to_i(self.high)