def verify_port_map(plugin):
    """
    extra validation /
    PB2 sees empty lists the same as non-existant lists
    :param plugin:
    :return:
    """
    result = True
    ex_ports = plugin.get(EX_PORTS_KEY)
    result &= isinstance(ex_ports, list) and verify_ports(ex_ports)
    in_ports = plugin.get(IN_PORTS_KEY)
    result &= isinstance(in_ports, list) and verify_ports(in_ports)
    env_list = plugin.get(ENV_KEY)
    result &= isinstance(env_list, list) and verify_environment(env_list)
    if result:
        result &= len(ex_ports) == len(in_ports)
    return result