:param container_port: The container port.
        :param proto: The protocol ('tcp' or 'udp').
        :param index: The index of the mapping entry to return.
        :returns: A tuple of the interface IP and port on the host.

def get_host_port(self, container_port, proto='tcp', index=0):
        """
        :param container_port: The container port.
        :param proto: The protocol ('tcp' or 'udp').
        :param index: The index of the mapping entry to return.
        :returns: A tuple of the interface IP and port on the host.
        """
        port_spec = '{}/{}'.format(container_port, proto)
        return self._host_port(port_spec, index)