class_docstr: An object that measures runtimes, accumulates them and computes
  a running fraction of the recent runtimes over the corresponding
  elapsed time.
class_docstr_tok: ["An","object","that","measures","runtimes",",","accumulates","them","and","computes","a","running","fraction","of","the","recent","runtimes","over","the","corresponding","elapsed","time","."]
code: def start_timing(self):
      assert self._cur_start is None
      self._cur_start = self._timer()
  
imports: from __future__ import annotations
  import gc
  import logging
  import threading
  from collections import deque
  import psutil
  from dask.utils import format_bytes
  from distributed.metrics import thread_time
label_desc: Use image node_id 3 for calling the FractionalTimer obj's underlying member method code with example usage: obj.start_timing() without return types