code: def start_main_loop(cls):
      # Set up a SIGINT handler to allow terminating a plot via CTRL-C.
      with _allow_interrupt_macos():
          _macosx.show()
  
imports: import os
  import matplotlib
  from matplotlib import _api, cbook
  from matplotlib._pylab_helpers import Gcf
  from .None import _macosx
  from .backend_agg import FigureCanvasAgg
  from matplotlib.backend_bases import _Backend, FigureCanvasBase, FigureManagerBase, NavigationToolbar2, ResizeEvent, TimerBase, _allow_interrupt
label_desc: Use image node_id 4 for calling the FigureManagerMac obj's underlying member method code with example usage: obj.start_main_loop(cls) without return types