String representation.

def to_string(self, verbose=0):
        """String representation."""
        lines = []
        app = lines.append
        app("<%s: %s>" % (self.__class__.__name__, self.basename))
        app("  summary: " + self.summary.strip())
        app("  number of valence electrons: %s" % self.Z_val)
        app("  maximum angular momentum: %s" % l2str(self.l_max))
        app("  angular momentum for local part: %s" % l2str(self.l_local))
        app("  XC correlation: %s" % self.xc)
        app("  supports spin-orbit: %s" % self.supports_soc)

        if self.isnc:
            app("  radius for non-linear core correction: %s" % self.nlcc_radius)

        if self.has_hints:
            for accuracy in ("low", "normal", "high"):
                hint = self.hint_for_accuracy(accuracy=accuracy)
                app("  hint for %s accuracy: %s" % (accuracy, str(hint)))

        return "\n".join(lines)