code: def set_display_mode(self, zoom,layout='continuous'):
          
          
          if(zoom=='fullpage' or zoom=='fullwidth' or zoom=='real' or zoom=='default' or not isinstance(zoom,basestring)):
              self.zoom_mode=zoom
          else:
              self.error('Incorrect zoom display mode: '+zoom)
          if(layout=='single' or layout=='continuous' or layout=='two' or layout=='default'):
              self.layout_mode=layout
          else:
              self.error('Incorrect layout display mode: '+layout)
docs: Set display mode in viewer
          
          The "zoom" argument may be 'fullpage', 'fullwidth', 'real',
          'default', or a number, interpreted as a percentage.