def __str__(self):
    Lines = []
    for o in self.Shells:
        Lines.append(('Atom %s  %s' % (o.Atom, o.Fn)))
    return '\n'.join(Lines)
def __str__(self):
    Lines = []
    for o in self.Shells:
        Lines.append(('Atom %s  %s' % (o.Atom, o.Fn)))
    return '\n'.join(Lines)