code: function raiseLevel(edge) {
    var s = edge.s
    var t = edge.t
  
    //Update position in edge lists
    removeEdge(s, edge)
    removeEdge(t, edge)
    edge.level += 1
    elist.insert(s.adjacent, edge)
    elist.insert(t.adjacent, edge)
    
    //Update flags for s
    if(s.euler.length <= edge.level) {
      s.euler.push(createEulerVertex(s))
    }
    var es = s.euler[edge.level]
    es.setFlag(true)
  
    //Update flags for t
    if(t.euler.length <= edge.level) {
      t.euler.push(createEulerVertex(t))
    }
    var et = t.euler[edge.level]
    et.setFlag(true)
  
    //Relink if necessary
    if(edge.euler) {
      edge.euler.push(es.link(et, edge))
    }
  }
docs: Raise the level of an edge, optionally inserting into higher level trees