code: function getMaxChildNodes(){
      var currentMaxNbChildren = 0;
      for (idNode in gNodesWithChildren){
          if(gNodesWithChildren.hasOwnProperty(idNode)){
              if (currentMaxNbChildren < gNodesWithChildren[idNode].length){
                  currentMaxNbChildren = gNodesWithChildren[idNode].length;
              }
          }
      }
      return currentMaxNbChildren;
  }
docs: Returns the max of child nodes (to draw a coherent graph)
  @returns {*}