Consider applying existing ordering of queryset, rather than requiring ordering as arg.

[adamkowalczyk]

CursorPaginator takes 2 parameters queryset and ordering and applies the ordering to the queryset on init.

However, if a query set is already adequately ordered for pagination purposes, either explicitly or on the model's Meta class, it would be convenient to be able to infer and user that ordering and to call CursorPaginator with a single queryset argument.

For example:

class CursorPaginator(object):

    def __init__(self, queryset, ordering=None):
        self.queryset = queryset
        self.ordering = ordering

        if ordering:
            self.queryset = queryset.order_by(*ordering)
        elif queryset.query.order_by:
            self.ordering = queryset.query.order_by
        elif queryset.query.get_meta().ordering
            self.ordering =  queryset.query.get_meta().ordering
        else:
            raise InvalidCursor('No ordering supplied of inferable')