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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def check(path_dir, requirements_name='requirements.txt'):
    '''Look for unused packages listed on project requirements'''
    requirements = _load_requirements(requirements_name, path_dir)
    imported_modules = _iter_modules(path_dir)
    installed_packages = _list_installed_packages()

    imported_modules.update(_excluded_imports())

    diff = {lib for lib in installed_packages if lib not in imported_modules}
    with_dependencies, _ = _list_dependencies(diff)
    unused_dependencies = sorted([d for d in diff if d in requirements])

    for unused_dependency in unused_dependencies:
        if with_dependencies.get(unused_dependency):
            print('    - {}'.format(unused_dependency))
            for dependency in with_dependencies.get(unused_dependency):
                print('\t - {}'.format(dependency))
        else:
            print('    - {}'.format(unused_dependency))