class_docstr: A class used for accessing tfdbg v2 DebugEvent data on local filesystem.
  
  This class is a short-term hack, mirroring the EventMultiplexer for the main
  TensorBoard plugins (e.g., scalar, histogram and graphs.) As such, it only
  implements the methods relevant to the Debugger V2 pluggin.
  
  TODO(cais): Integrate it with EventMultiplexer and use the integrated class
  from MultiplexerDataProvider for a single path of accessing debugger and
  non-debugger data.
docstr: Return the timestamp of the first DebugEvent of the given run.
  
  This may perform I/O if no events have been loaded yet for the run.
  
  Args:
    run: A string name of the run for which the timestamp is retrieved.
      This currently must be hardcoded as `DEFAULT_DEBUGGER_RUN_NAME`,
      as each logdir contains at most one DebugEvent file set (i.e., a
      run of a tfdbg2-instrumented TensorFlow program.)
  
  Returns:
      The wall_time of the first event of the run, which will be in seconds
      since the epoch as a `float`.
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code: def FirstEventTimestamp(self, run):
      """Return the timestamp of the first DebugEvent of the given run.
  
      This may perform I/O if no events have been loaded yet for the run.
  
      Args:
        run: A string name of the run for which the timestamp is retrieved.
          This currently must be hardcoded as `DEFAULT_DEBUGGER_RUN_NAME`,
          as each logdir contains at most one DebugEvent file set (i.e., a
          run of a tfdbg2-instrumented TensorFlow program.)
  
      Returns:
          The wall_time of the first event of the run, which will be in seconds
          since the epoch as a `float`.
      """
      if self._reader is None:
          raise ValueError("No tfdbg2 runs exists.")
      if run != DEFAULT_DEBUGGER_RUN_NAME:
          raise ValueError(
              "Expected run name to be %s, but got %s"
              % (DEFAULT_DEBUGGER_RUN_NAME, run)
          )
      return self._reader.starting_wall_time()
  
imports: import threading
  from tensorboard import errors
label_desc: Use image node_id 4 for calling the DebuggerV2EventMultiplexer obj's underlying member method code with example usage: obj.FirstEventTimestamp(run) and returns: self