parameters: (plugin_init_func, plugin_name=None, plugin_module=None)
docstring: Register a plugin.
  
      @param plugin: a callable object that will be invoked whenever a
      Visualizer object is created, like this: plugin(visualizer)
docstring_summary: Register a plugin.
docstring_tokens: Register a plugin .
function: def register_plugin(plugin_init_func, plugin_name=None, plugin_module=None):
      """
      Register a plugin.
  
      @param plugin: a callable object that will be invoked whenever a
      Visualizer object is created, like this: plugin(visualizer)
      """
      assert callable(plugin_init_func)
      plugins.append(plugin_init_func)
      if plugin_module is not None:
          plugin_modules[plugin_name] = plugin_module
function_tokens: def register_plugin ( plugin_init_func , plugin_name = None , plugin_module = None ) : assert callable ( plugin_init_func ) plugins . append ( plugin_init_func ) if plugin_module is not None : plugin_modules [ plugin_name ] = plugin_module