'List a Tag\'s Values
Return a list of values associated with this key for an issue.
:pparam string issue_id: the ID of the issue to retrieve.
:pparam string key: the tag key to look the values up for.
:auth: required'

def get(self, request, group, key):

    if TagKey.is_reserved_key(key):
        lookup_key = 'sentry:{0}'.format(key)
    else:
        lookup_key = key
    tagkey = TagKey.objects.filter(project=group.project_id, key=lookup_key, status=TagKeyStatus.VISIBLE)
    if (not tagkey.exists()):
        raise ResourceDoesNotExist
    queryset = GroupTagValue.objects.filter(group_id=group.id, key=lookup_key)
    sort = request.GET.get('sort')
    if (sort == 'date'):
        order_by = '-last_seen'
        paginator_cls = DateTimePaginator
    elif (sort == 'age'):
        order_by = '-first_seen'
        paginator_cls = DateTimePaginator
    elif (sort == 'freq'):
        order_by = '-times_seen'
        paginator_cls = OffsetPaginator
    else:
        order_by = '-id'
        paginator_cls = Paginator
    if (key == 'user'):
        serializer_cls = UserTagValueSerializer()
    else:
        serializer_cls = None
    return self.paginate(request=request, queryset=queryset, order_by=order_by, paginator_cls=paginator_cls, on_results=(lambda x: serialize(x, request.user, serializer_cls)))
