class BridgeContext(object):
    def setUp(self):
        """Create a bridge and returns it."""
    self.addCleanup(self.destroy)

    @abc.abstractmethod
    def destroy(self):
        """Delete a bridge."""

    @abc.abstractmethod
    def create_port_in_ns(self, ns_ip_wrapper):
        """Returns a context for creating a port in a specific namespace.
        The context creates a port in a specifc namespace on __enter__ and
                    deletes it on __exit__.
        """