code: def main():
      watcher = WatcherBase()
      line_plot = LinePlot()
      stream = watcher.create_stream(expr="lambda vars:vars.x")
      line_plot.subscribe(stream)
      line_plot.show()
  
      for i in range(5):
          watcher.observe(x=(i, i * i))
      plt_loop()
  
imports: from tensorwatch.watcher_base import WatcherBase
  from tensorwatch.mpl.line_plot import LinePlot
  from tensorwatch.image_utils import plt_loop
  from tensorwatch.stream import Stream
  from tensorwatch.lv_types import StreamItem
label_desc: Use image node_id 1 for calling a global function with example usage: main() without return types