-- | Removes node groups which can't accommodate the instance
filterValidGroups :: [(Group.Group, (Node.List, Instance.List))]
                  -> Instance.Instance
                  -> ([(Group.Group, (Node.List, Instance.List))], [String])
filterValidGroups [] _ = ([], [])
filterValidGroups :: [(Group.Group, (Node.List, Instance.List))]
                  -> Instance.Instance
                  -> ([(Group.Group, (Node.List, Instance.List))], [String])
filterValidGroups [] _ = ([], [])
filterValidGroups [] _ = ([], [])