def import_submodules(package):
    """Return list of imported module instances from beneath root_package"""

    if isinstance(package, str):
        package = importlib.import_module(package)

    results = {}

    for _, full_name, is_pkg in pkgutil.walk_packages(package.__path__, package.__name__ + '.'):
        results[full_name] = importlib.import_module(full_name)

        if is_pkg:
            results.update(import_submodules(full_name))

    return results