'TableEntry' object has no attribute 'metadata'

[yhx-coder]

when I used SimpleSwitchP4RuntimeAPI.table_add() to insert some entries, an exception occurred in the p4runtime_API api.py _EntityBase._write() and said TableEntry object has no attribute metadata. The program is roughly the same as p4-learning/exercises/08-Simple_Routing/p4runtime/solution/routing-controller.py. The tables show below:

table ipv4_lpm {
    key = {
        hdr.ipv4.dstAddr: lpm;
    }
    actions = {
        ipv4_forward;
        drop;
        NoAction;
    }
    size = 1024;
    default_action = drop();
}
table l2_exact_table {
    key = {
        hdr.ethernet.dstAddr: exact;
    }
    actions = {
        set_egress_port;
        send_to_CPU;
        drop;
        NoAction;
    }
    default_action = NoAction;
}

i wonder what the metadata means. I find it in the class TableEntry . could someone help me? thanks a lot.