setCurrent (current) {
    if (this.current !== current) {
      this.current = current;
      if (current) {
        this.loadedOnce = true;
        this.validateState();
        this.validateLayout();
        this.emitObjectUpdated();
      } else {
        each(this.connections, connection => connection.cleanup());
        each(this.nodes, node => node.cleanup());
      }
      this._particleSystem.setLastUpdateTime(getPerformanceNow());
      this.updateIsParticleSystemEnabled();
    }
  }
Set whether this graph is the currently displayed graph or not.
This is important to call for the newly current graph so that it can update properly,
and important to call for the previous graph so we can cleanup any renderers that we
don't need to keep around

@param {boolean} current Whether to set this graph as current or not