Retrieve a list of plugins in the PluginManager.
        All plugins if no arguments are provides, or of the specified type.
        :param plugin_type: list: Types of plugins to retrieve from the plugin manager.
        :return: Plugins being managed by the Manager (optionally of the desired plugin_type).
        :rtype: list

def get_plugins(self, plugin_type=None):
        """
        Retrieve a list of plugins in the PluginManager.
        All plugins if no arguments are provides, or of the specified type.
        :param plugin_type: list: Types of plugins to retrieve from the plugin manager.
        :return: Plugins being managed by the Manager (optionally of the desired plugin_type).
        :rtype: list
        """
        if plugin_type is None:
            return self.plugins.values()

        plugin_list = []
        for name, plugin in self.plugins.items():
            if isinstance(plugin, plugin_type if inspect.isclass(plugin_type) else type(plugin_type)):
                plugin_list.append(plugin)

        return plugin_list