code: def get_timestamps(trials, size, space_type):
      """Get start timestamps of the trials
  
      Parameters
      ----------
      trials: `list` of `orion.core.worker.trial.Trial`
          List of all trials at the end of the stress test
      space_type: str
          See `get_experiment`.
      size: int
          See `get_experiment`.
  
      Returns
      -------
      (`list`, `list`)
          Where rval[0] is start timestamp and rval[1] is the index of the trial.
          For instance the i-th trial timestamp is rval[0][rval[1].index(i)].
  
      """
      hparams = set()
      x = []
      y = []
  
      start_time = None
      for i, trial in enumerate(trials):
          hparams.add(trial.params["x"])
          assert trial.objective.value == trial.params["x"]
          if start_time is None:
              start_time = trial.submit_time
          x.append((trial.submit_time - start_time).total_seconds())
          y.append(i)
  
      if space_type in ["discrete", "real-seeded"]:
          assert len(hparams) == size
      else:
          assert len(hparams) >= size
  
      return x[:size], y[:size]
  
file_path: orion/tests/stress/client/stress_experiment.py
imports: import os
  import random
  import time
  import traceback
  from multiprocessing import Pool
  import matplotlib.pyplot
  from pymongo import MongoClient
  from orion.client import create_experiment
  from orion.core.io.database import DatabaseTimeout
  from orion.core.utils.exceptions import ReservationTimeout
label_desc: Use image node_id 5 for calling a global function with example usage: get_timestamps(trials, size, space_type) and returns: x,  y