How I can override virtualNic adapter defaultGateway using pyvmomi?

Question

Here is the code As I have already created virtual nic on host I am trying to use updateVirtualNic method configManager.networkSystem

    vnic_config = vim.host.VirtualNic.Specification()
    vnic_config.ipRouteSpec = vim.host.VirtualNic.IpRouteSpec()
    vnic_config.ipRouteSpec.ipRouteConfig = vim.host.IpRouteConfig()
    vnic_config.ipRouteSpec.ipRouteConfig.defaultGateway = gateway
    try:
        host_obj.configManager.networkSystem.UpdateVirtualNic('vmk1', vnic_config)
    except Exception as e:
        self.args.rt.comment(e.msg)
        return False
    return True