def cfg_convert(self, value):
            """Default converter for the cfg:// protocol."""
            rest = value
            m = self.WORD_PATTERN.match(rest)
            if m is None:
                raise ValueError("Unable to convert %r" % value)
            else:
                rest = rest[m.end():]
                d = self.config[m.groups()[0]]
                #print d, rest
                while rest:
                    m = self.DOT_PATTERN.match(rest)
                    if m:
                        d = d[m.groups()[0]]
                    else:
                        m = self.INDEX_PATTERN.match(rest)
                        if m:
                            idx = m.groups()[0]
                            if not self.DIGIT_PATTERN.match(idx):
                                d = d[idx]
                            else:
                                try:
                                    n = int(idx) # try as number first (most likely)
                                    d = d[n]
                                except TypeError:
                                    d = d[idx]
                    if m:
                        rest = rest[m.end():]
                    else:
                        raise ValueError('Unable to convert '
                                         '%r at %r' % (value, rest))
            #rest should be empty
            return d
Default converter for the cfg:// protocol.
product/gradle-plugin/src/main/python/pip/_vendor/distlib/compat.py