code: function setViewProvider(p){
              if (this.provider != p) {
                  this.stopEditing(false);
                  this.provider = p;
                  delete this.nodes;
                  this.nodes = {};
                  this.vrp();
              }
              return this;
          }
docs: Set tree component items view provider. Provider says how tree model items
  have to be visualized.
  @param {zebkit.ui.tree.DefViews} p a view provider
  @method setViewProvider
  @chainable