code: public VirtualRouterSpec withListeners(VirtualRouterListener... listeners) {
          if (this.listeners == null) {
              setListeners(new java.util.ArrayList<VirtualRouterListener>(listeners.length));
          }
          for (VirtualRouterListener ele : listeners) {
              this.listeners.add(ele);
          }
          return this;
      }
docs: <p>
  The listeners that the virtual router is expected to receive inbound traffic from. Currently only one listener is
  supported per virtual router.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setListeners(java.util.Collection)} or {@link #withListeners(java.util.Collection)} if you want to
  override the existing values.
  </p>
  
  @param listeners
  The listeners that the virtual router is expected to receive inbound traffic from. Currently only one
  listener is supported per virtual router.
  @return Returns a reference to this object so that method calls can be chained together.