code: def get_run_time_period(run_steps):
    
    init_ts_start = get_standardized_timestamp('now', None)
    ts_start = init_ts_start
    ts_end = '0'
    for run_step in run_steps:
      if run_step.ts_start and run_step.ts_end:
        if run_step.ts_start < ts_start:
          ts_start = run_step.ts_start
        if run_step.ts_end > ts_end:
          ts_end = run_step.ts_end
    if ts_end == '0':
      ts_end = None
    if ts_start == init_ts_start:
      ts_start = None
    logger.info('get_run_time_period range returned ' + str(ts_start) + ' to ' + str(ts_end))
    return ts_start, ts_end
docs: This method finds the time range which covers all the Run_Steps
  
    :param run_steps: list of Run_Step objects
    :return: tuple of start and end timestamps