True if element is a transition metal.

def is_transition_metal(self):
        """
        True if element is a transition metal.
        """
        ns = list(range(21, 31))
        ns.extend(list(range(39, 49)))
        ns.append(57)
        ns.extend(list(range(72, 81)))
        ns.append(89)
        ns.extend(list(range(104, 113)))
        return self.Z in ns