Converts pygmets style to urwid palatte

def register_palette(self):
        """Converts pygmets style to urwid palatte"""
        default = 'default'
        palette = list(self.palette)
        mapping = CONFIG['rgb_to_short']
        for tok in self.style.styles.keys():
            for t in tok.split()[::-1]:
                st = self.style.styles[t]
                if '#' in st:
                    break
            if '#' not in st:
                st = ''
            st = st.split()
            st.sort()   # '#' comes before '[A-Za-z0-9]'
            if len(st) == 0:
                c = default
            elif st[0].startswith('bg:'):
                c = default
            elif len(st[0]) == 7:
                c = 'h' + rgb_to_short(st[0][1:], mapping)[0]
            elif len(st[0]) == 4:
                c = 'h' + rgb_to_short(st[0][1]*2 + st[0][2]*2 + st[0][3]*2, mapping)[0]
            else:
                c = default
            a = urwid.AttrSpec(c, default, colors=256)
            row = (tok, default, default, default, a.foreground, default)
            palette.append(row)
        self.loop.screen.register_palette(palette)