def features(self):
        """List of features."""

        r = []
        for _, inter in self.props.items():
            if isinstance(inter, tuple):
                if (inter[0] and inter[1] and inter[0].getValue() == inter[1].getValue() and
                        inter[0].operator == "=" and inter[1].operator == "="):
                    r.append(inter[0])
                else:
                    r.extend([f for f in inter if f])
            elif isinstance(inter, dict):
                r.extend(inter.values())
            elif isinstance(inter, list):
                r.extend(inter)
            else:
                r.append(inter)
        return r
List of features.