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(backend_agg.FigureCanvasAgg)
      return agg.print_png(filename, *args, **kwargs)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import numpy
  import warnings
  from .None import backend_agg, backend_gtk3
  from .backend_cairo import cairo, HAS_CAIRO_CFFI
  from .backend_gtk3 import _BackendGTK3
  from matplotlib import transforms
label_desc: Use image node_id 6 for calling the FigureCanvasGTK3Agg obj's underlying member method code with example usage: obj.print_png(filename) and returns: agg