class_docstr: Save the model once triggered.
class_docstr_tok: ["Save","the","model","once","triggered","."]
code: def _before_train(self):
      # graph is finalized, OK to write it now.
      time = datetime.now().strftime("%m%d-%H%M%S")
      self.saver.export_meta_graph(
          os.path.join(
              self.checkpoint_dir, "graph-{}.meta".format(time)
          ),
          collection_list=self.graph.get_all_collection_keys(),
      )
  
file_path: tensorpack/tensorpack/callbacks/saver.py
imports: import os
  from datetime import datetime
  from ..compat import tfv1
  from ..utils import fs, logger
  from .base import Callback
label_desc: Use image node_id 3 for calling the ModelSaver obj's underlying member method code with example usage: obj._before_train() without return types