new_contents: from IPython.core.magic import Magics, magics_class, line_magic
  from IPython.core.display import display_png
  
  
  @magics_class
  class AbjadMagic(Magics):
  
      @line_magic
      def show(self, line=''):
          display_png(open('/home/tra/.abjad/output/%s' % '0010.preview.png',
                           'rb').read(),
                      raw=True)
  
  
  def load_ipython_extension(ip):
      """Load the extension in IPython."""
      global _loaded
      if not _loaded:
          ip.register_magics(AbjadMagic)
          _loaded = True
  
  _loaded = False
  
subject: read a png