Make camelCase variant of value.

def make_key(self, value):
        """ Make camelCase variant of value. """
        if value:
            parts = [self.key_filter.sub('', x)
                     for x in self.key_split.split(value.lower())]
            key = parts[0] + ''.join(map(str.capitalize, parts[1:]))
        else:
            key = ''
        if key in self.seen_keys:
            i = 1
            while '%s%d' % (key, i) in self.seen_keys:
                i += 1
            key = '%s%d' % (key, i)
        self.seen_keys.add(key)
        return key