'Create a non-vlan bridge unless it already exists.'

def ensure_flat_bridge(self, network_id, phy_bridge_name, physical_interface):

    if phy_bridge_name:
        return self.ensure_bridge(phy_bridge_name)
    else:
        bridge_name = self.get_bridge_name(network_id)
        if self.ensure_bridge(bridge_name, physical_interface):
            return physical_interface
