private static List<String> resolveMemberShapes(MemberModel member) {

        if (member == null) return new LinkedList<String>();
        if (member.getEnumType() != null) {
            return Collections.singletonList(member.getEnumType());
        } else if (member.isList()) {
            return resolveMemberShapes(member.getListModel().getListMemberModel());
        } else if (member.isMap()) {
            List<String> memberShapes = new LinkedList<String>();
            memberShapes.addAll(resolveMemberShapes(member.getMapModel().getKeyModel()));
            memberShapes.addAll(resolveMemberShapes(member.getMapModel().getValueModel()));
            return memberShapes;
        } else if (member.isSimple()) {
            // member is scalar, do nothing
            return new LinkedList<String>();
        } else {
            // member is a structure.
            return Collections.singletonList(member.getVariable().getSimpleType());
        }
    }
Recursively resolves the shapes represented by the member. When the member is a map,
both the key shape and the value shape of the map will be resolved, so that the
returning list could have more than one elements.
aws-java-sdk-code-generator/src/main/java/com/amazonaws/codegen/RemoveUnusedShapes.java