docstr: Sets tracing attribute True only if the request cache is empty.
  If `trace_once()` is called again, it sets tracing attribute to False
docstr_tok: ["Sets","tracing","attribute","True","only","if","the","request","cache","is","empty",".","If","`","trace_once","(",")","`","is","called","again",",","it","sets","tracing","attribute","to","False"]
code: def trace_once(self):
      """Sets tracing attribute True only if the request cache is empty.
      If `trace_once()` is called again, it sets tracing attribute to False
      """
      untraced = self.request_cache.empty()
      self.trace(tracing=untraced)
  
imports: import os
  import crypten
  import crypten.communicator
  import torch
label_desc: Use image node_id 6 for calling the TupleProvider obj's underlying member method code with example usage: obj.trace_once() without return types