code: def mpl_history_plot():
      cli = tw.WatcherClient()
      p2 = tw.LinePlot(title="History Demo")
      p2s1 = cli.create_stream(
          event_name="ev_j",
          expr="map(lambda v:(v.val, math.sqrt(v.val)*2), l)",
      )
      p2.subscribe(
          p2s1,
          xtitle="Index",
          ytitle="sqrt(ev_j)",
          clear_after_end=True,
          history_len=15,
      )
      p2.show()
      tw.plt_loop()
  
file_path: tensorwatch/test/simple_log/cli_ij.py
imports: import tensorwatch
  import time
  import math
  from tensorwatch import utils
label_desc: Use image node_id 2 for calling a global function with example usage: mpl_history_plot() without return types