def find_plugins():
    load_plugins()
    plugins = []
    for cls in _classes:
        # Only instantiate each plugin class once.
        if cls not in _instances:
            _instances[cls] = cls()
        plugins.append(_instances[cls])
    return plugins


# Communication with plugins.
Returns a list of BeetsPlugin subclass instances from all
dataset/ETHPy150Open beetbox/beets/beets/plugins.py/find_plugins