experimental options used by profiler libraries like Kineto.
        Note, backward compatibility is not guaranteed.
Note:
 This API is experimental and subject to change in the
 future.Enabling shape and stack tracing results in additional
 overhead. When record_shapes=True is specified, profiler will
 temporarily hold references to the tensors; that may further
 prevent certain optimizations that depend on the reference count
 and introduce extra tensor copies.

add_metadata(key, value)
  Adds a user defined metadata with a string key and a string
  value into the trace file

add_metadata_json(key, value)
  Adds a user defined metadata with a string key and a valid json
  value into the trace file

events()
  Returns the list of unaggregated profiler events, to be used in
  the trace callback or after the profiling is finished

export_chrome_trace(path)
  Exports the collected trace in Chrome JSON format.
