QuerySet wrapper

class QuerySet(object):
    def __init__(self, query=None):
        self.query = query or {}

    def _clone(self):
        return type(self)(query=deepcopy(self.query))

    def __getitem__(self, k):
        if isinstance(k, slice):

    def all(self):
        return self._clone()

    def filter(self, **kwargs):
        clone = self._clone()
        clone.query.update(kwargs)
        return clone

    def count(self):
        raise NotImplementedError()

    def exists(self):
        raise NotImplementedError()

    def get(self, *args, **kwargs):
        raise NotImplementedError()

    def order_by(self, *field_names):
        raise NotImplementedError()

    def distinct(self, *field_names):
        raise NotImplementedError()