-record(worker, {
    id :: integer(),
    pid :: gleam@erlang@process:pid_(),
    batch_inbox :: gleam@erlang@process:subject(viva_tensor@distributed@trainer:worker_message()),
    grads_outbox :: gleam@erlang@process:subject({integer(),
        integer(),
        list(viva_tensor@nn@optim:grad_pair())})
}).