class_docstr: A task to start
class_docstr_tok: ["A","task","to","start"]
docstr: The duration according to cpu clock time
docstr_tok: ["The","duration","according","to","cpu","clock","time"]
code: def cpu_duration(self) -> Optional[float]:
      """The duration according to cpu clock time"""
      if self.cpu_start and self.cpu_end:
          return self.cpu_end - self.cpu_start
      else:
          return None
  
imports: from __future__ import annotations
  from typing import Iterator, Mapping, Optional, Tuple
  import sys
  import time
  from contextlib import contextmanager
  from itertools import repeat
  from typing_extensions import Literal
label_desc: Use image node_id 6 for calling the TimingTask obj's underlying member method code with example usage: obj.cpu_duration() and returns: unknown, None