Atomically increment ``qfield`` by ``value``

def inc(self, *args, **kwargs):
        ''' Atomically increment ``qfield`` by ``value`` '''
        pairs = []
        if len(args) == 1:
            pairs.append((args[0], 1))
        elif len(args) == 2:
            pairs.append(args)
        elif len(kwargs) != 0:
            pairs.extend([(k, v) for k, v in kwargs.items()])
        else:
            raise UpdateException('Invalid arguments for set.  Requires either two positional arguments or at least one keyword argument')

        ret = self
        for qfield, value in pairs:
            ret = self._atomic_op('$inc', qfield, value)
        return ret