code: def output_subplot_array(output_path, output_filename, output_format):
      
      if output_format is 'show':
          plt.show()
      elif output_format is 'png':
          plt.savefig(output_path + output_filename + '.png', bbox_inches='tight')
      elif output_format is 'fits':
          raise exc.PlottingException('You cannot output a subplots with format .fits')
docs: Output a figure which consists of a set of subplot,, either as an image on the screen or to the hard-disk as a \
      .png file.
  
      Parameters
      -----------
      output_path : str
          The path on the hard-disk where the figure is output.
      output_filename : str
          The filename of the figure that is output.
      output_format : str
          The format the figue is output:
          'show' - display on computer screen.
          'png' - output to hard-disk as a png.