code: def mpl_line_plot():
      cli = tw.WatcherClient()
      p = tw.LinePlot(title="Demo")
      s1 = cli.create_stream(
          event_name="ev_i", expr="map(lambda v:math.sqrt(v.val)*2, l)"
      )
      p.subscribe(s1, xtitle="Index", ytitle="sqrt(ev_i)")
      p.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 1 for calling a global function with example usage: mpl_line_plot() without return types