code: def add_default_plugins(self, except_global=[], except_local=[]):
          
          # add default global plugins
          for spec in plugins:
              ptype = spec.get('ptype', 'local')
              if ptype == 'global' and spec.module not in except_global:
                  self.add_plugin_spec(spec)
  
              if ptype == 'local' and spec.module not in except_local:
                  self.add_plugin_spec(spec)
docs: Add the ginga-distributed default set of plugins to the
          reference viewer.