code: def print_png(self, filename, *args, **kwargs):
      # Do this so we can save the resolution of figure in the PNG file
      agg = self.switch_backends(FigureCanvasAgg)
      return agg.print_png(filename, *args, **kwargs)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import matplotlib
  from matplotlib.cbook import warn_deprecated
  from matplotlib.backends.backend_agg import FigureCanvasAgg
  from matplotlib.backends.backend_gtk import gtk, _BackendGTK, FigureCanvasGTK, FigureManagerGTK, NavigationToolbar2GTK, backend_version, error_msg_gtk, PIXELS_PER_INCH
  from matplotlib.backends._gtkagg import agg_to_gtk_drawable
label_desc: Use image node_id 5 for calling the FigureCanvasGTKAgg obj's underlying member method code with example usage: obj.print_png(filename) and returns: agg