Find packages that are plugins of the given package.

    Args:
        package_name (str): Name of the package.
        paths (list of str): Paths to search for packages, defaults to
            `config.packages_path`.

    Returns:
        list of str: The packages that are plugins of the given package.

def get_plugins(package_name, paths=None):
    """Find packages that are plugins of the given package.

    Args:
        package_name (str): Name of the package.
        paths (list of str): Paths to search for packages, defaults to
            `config.packages_path`.

    Returns:
        list of str: The packages that are plugins of the given package.
    """
    pkg = get_latest_package(package_name, paths=paths, error=True)
    if not pkg.has_plugins:
        return []

    it = iter_package_families(paths)
    package_names = set(x.name for x in it)
    bar = ProgressBar("Searching", len(package_names))

    plugin_pkgs = []
    for package_name_ in package_names:
        bar.next()
        if package_name_ == package_name:
            continue  # not a plugin of itself

        plugin_pkg = get_latest_package(package_name_, paths=paths)
        if not plugin_pkg.plugin_for:
            continue
        for plugin_for in plugin_pkg.plugin_for:
            if plugin_for == pkg.name:
                plugin_pkgs.append(package_name_)

    bar.finish()
    return plugin_pkgs