How to use the ext/splitview/splits.mutate function in ext

return ret;
        }
        else if (shiftKey) {
            // enable split view ONLY for code editors for now...
            if (!this.isSupportedEditor(activePage.$editor, page.$editor))
                return;
            // tabs can be merged into and unmerged from a splitview by clicking a
            // tab while holding shift
            //console.log("is clone?",apf.isTrue(page.$doc.getNode().getAttribute("clone")));
            if (apf.isTrue(page.$doc.getNode().getAttribute("clone"))) {
                tabs.remove(page, null, true);
                ret = false;
            }
            else {
                ret = !splits.mutate(split, page);
                this.save();
            }
            return ret;
        }
    },

return;
            // tabs can be merged into and unmerged from a splitview by clicking a
            // tab while holding shift
            //console.log("is clone?",apf.isTrue(page.$doc.getNode().getAttribute("clone")));
            if (split && apf.isTrue(page.$doc.getNode().getAttribute("clone"))) {
                // close the page that contains the clone editor
                var cloneEditor = Splits.getCloneEditor(page);
                for (i = 0, l = split.pairs.length; i < l; ++i) {
                    if (split.pairs[i].editor !== cloneEditor)
                        continue;
                    tabs.remove(split.pairs[i].page, null, true);
                    return false;
                }
            }
            else {
                ret = !Splits.mutate(split, page);
                this.save();
            }
            return ret;
        }
    },

// if the max amount of tabs has been reached inside a split view,
            // then the user may remove the last or first tab from it.
            idx = pages.indexOf(split.pairs[bRight ? splitLen - 1 : 0].page);
        }
        else {
            var currIdx = pages.indexOf(curr);
            idx = currIdx + (bRight ? 1 : -1);
        }
        if (idx < 0 || idx > pages.length - 1)
            return;

        // enable split view ONLY for code editors for now...
        if (!this.isSupportedEditor(curr.$editor, pages[idx].$editor))
            return;
        // pass in null to mutate the active split view
        splits.mutate(null, pages[idx]);
        splits.update();
        this.save();
        return false;
    },

// if the max amount of tabs has been reached inside a split view,
            // then the user may remove the last or first tab from it.
            idx = pages.indexOf(split.pairs[bRight ? splitLen - 1 : 0].page);
        }
        else {
            var currIdx = pages.indexOf(curr);
            idx = currIdx + (bRight ? 1 : -1);
        }
        if (idx < 0 || idx > pages.length - 1)
            return;

        // enable split view ONLY for code editors for now...
        if (!this.isSupportedEditor(curr.$editor, pages[idx].$editor))
            return;
        // pass in null to mutate the active split view
        Splits.mutate(null, pages[idx]);
        Splits.update(Splits.getActive());
        this.save();
        return false;
    },

tabs.set(split.pairs[0].page);
                ret = false;
            }
            
            if (!shiftKey)
                return true;

            return ret;
        }
        else if (shiftKey) {
            // enable split view ONLY for code editors for now...
            if (page.$editor.name.indexOf("Code Editor") == -1)
                return;
            // tabs can be merged into and unmerged from a splitview by clicking a
            // tab while holding shift
            ret = !Splits.mutate(split, page);
            this.save();
            return ret;
        }
    },

// if the max amount of tabs has been reached inside a split view,
            // then the user may remove the last or first tab from it.
            idx = pages.indexOf(split.pairs[bRight ? splitLen - 1 : 0].page);
        }
        else {
            var currIdx = pages.indexOf(curr);
            idx = currIdx + (bRight ? 1 : -1);
        }
        if (idx < 0 || idx > pages.length - 1)
            return;

        // enable split view ONLY for code editors for now...
        if (pages[idx].$editor.name.indexOf("Code Editor") == -1)
            return;
        // pass in null to mutate the active split view
        Splits.mutate(null, pages[idx]);
        Splits.update();
        this.save();
        return false;
    },

onFileClose: function(e) {
        var page = e.page;
        var splits = Splits.get(page);
        for (var i = 0, l = splits.length; i < l; ++i)
            Splits.mutate(splits[i], page);
        this.save();
    },

fake.setAttribute("tooltip", "[@path]");
        fake.setAttribute("class",
            "{parseInt([@saving], 10) || parseInt([@lookup], 10) ? (tabEditors.getPage(tabEditors.activepage) == this ? 'saving_active' : 'saving') : \
            ([@loading] ? (tabEditors.getPage(tabEditors.activepage) == this ? 'loading_active' : 'loading') : '')}"
        );
        fake.setAttribute("model", fake.$model = page.$model);
        
        page.addEventListener("DOMNodeRemovedFromDocument", function(e) {
            if (typeof tabEditors == "undefined" || !fake || !fake.parentNode)
                return;
            tabEditors.remove(fake);
        });
        
        Editors.initEditorEvents(fake, page.$model);
        
        Splits.mutate(null, fake);
        
        split = Splits.get(fake)[0];
        split.clone = fake;
        
        Splits.update(split);
        
        this.save();
        
        return fake;
    },

if (page) {
                        if (!pageSet) {
                            tabs.set(page);
                            pageSet = true;
                        }
                        this.startCloneView(page);
                    }
                }
                else {
                    page = tabs.getPage(ids[j]);
                    if (page) {
                        if (!pageSet) {
                            tabs.set(page);
                            pageSet = true;
                        }
                        Splits.mutate(null, page);
                    }
                }
            }
            if (gridLayout)
                Splits.update(null, gridLayout);

            if (apf.isTrue(nodes[i].getAttribute("active")))
                active = Splits.getActive();
        }
        
        if (!active || Splits.indexOf(active, activePage) == -1)
            tabs.set(activePage);
        else
            Splits.show(active);
    },

onFileClose: function(e) {
        var page = e.page;
        var splits = Splits.get(page);
        for (var i = 0, l = splits.length; i < l; ++i)
            Splits.mutate(splits[i], page);
        Splits.update();
        this.save();
    },