flow(flow) {
    if (typeof flow != "undefined") {
      if (flow === "scrolled" || flow === "scrolled-continuous" || flow === "scrolled-doc") {
        this._flow = "scrolled";
      } else {
        this._flow = "paginated";
      } // this.props.flow = this._flow;


      this.update({
        flow: this._flow
      });
    }

    return this._flow;
  }
Switch the flow between paginated and scrolled
@param  {string} flow paginated | scrolled
@return {string} simplified flow