message: [pybind11] add support for begin_trace and end_trace
  With this change pybind11 performance matches cffi.
diff: @@ -62,6 +62,8 @@ void fit(FFModel &model, SingleDataLoader &x, SingleDataLoader &y, int epochs)
  {
  int num_samples = y.num_samples;
  int batch_size = model.config.batchSize;
  + static int tracing_id = 200;
  + tracing_id ++;
  for (int epoch = 0; epoch < epochs; epoch++) {
  x.reset();
  y.reset();
  @@ -70,10 +72,12 @@ void fit(FFModel &model, SingleDataLoader &x, SingleDataLoader &y, int epochs)
  for (int iter = 0; iter < iterations; iter++) {
  x.next_batch(model);
  y.next_batch(model);
  + model.config.lg_hlr->begin_trace(model.config.lg_ctx, tracing_id);
  model.forward();
  model.zero_gradients();
  model.backward();
  model.update();
  + model.config.lg_hlr->end_trace(model.config.lg_ctx, tracing_id);
  }
  }
  }
  @@ -124,6 +128,8 @@ PYBIND11_MODULE(flexflow_bindings, m) {
  .def_readonly("epochs", &FFConfig::epochs)
  .def_readonly("num_nodes", &FFConfig::numNodes)
  .def_readonly("workers_per_node", &FFConfig::workersPerNode)
  + .def("begin_trace", [](FFConfig &config, int trace_id) { config.lg_hlr->begin_trace(config.lg_ctx, trace_id); })
  + .def("end_trace", [](FFConfig &config, int trace_id) { config.lg_hlr->end_trace(config.lg_ctx, trace_id); })
  .def("get_current_time", &get_current_time);
  py::enum_<CompMode>(m, "CompMode")
  