class_docstr: Loader for a root log directory, maintaining multiple DirectoryLoaders.
  
  This class takes a root log directory and a factory for DirectoryLoaders, and
  maintains one DirectoryLoader per "logdir subdirectory" of the root logdir.
  
  Note that this class is not thread-safe.
docstr: Returns tf.Event generators for each run's `DirectoryLoader`.
  
  Warning: the generators are stateful and consuming them will affect the
  results of any other existing generators for that run; calling code should
  ensure it takes events from only a single generator per run at a time.
  
  Returns:
    Dictionary containing an entry for each run, mapping the run name to a
    generator yielding tf.Event protobuf objects loaded from that run.
code: def get_run_events(self):
      """Returns tf.Event generators for each run's `DirectoryLoader`.
  
      Warning: the generators are stateful and consuming them will affect the
      results of any other existing generators for that run; calling code should
      ensure it takes events from only a single generator per run at a time.
  
      Returns:
        Dictionary containing an entry for each run, mapping the run name to a
        generator yielding tf.Event protobuf objects loaded from that run.
      """
      runs = list(self._directory_loaders)
      logger.info(
          "Creating event loading generators for %d runs", len(runs)
      )
      run_to_loader = collections.OrderedDict()
      for run_name in sorted(runs):
          loader = self._directory_loaders[run_name]
          run_to_loader[run_name] = self._wrap_loader_generator(
              loader.Load()
          )
      return run_to_loader
  
file_path: tensorboard/tensorboard/uploader/logdir_loader.py
imports: import collections
  import os
  from tensorboard.backend.event_processing import directory_watcher
  from tensorboard.backend.event_processing import io_wrapper
  from tensorboard.util import tb_logging
label_desc: Use image node_id 3 for calling the LogdirLoader obj's underlying member method code with example usage: obj.get_run_events() and returns: run_to_loader