How to use the mlblocks.discovery.load_pipeline function in mlblocks

def test__load_pipeline_value_error(load_mock, gpp_mock):
    load_mock.return_value = None
    gpp_mock.return_value = ['a', 'b']

    with pytest.raises(ValueError):
        discovery.load_pipeline('invalid.pipeline')

    load_mock.assert_called_once_with('invalid.pipeline', ['a', 'b'])

def test__load_pipeline_success(load_mock, gpp_mock):
    gpp_mock.return_value = ['a', 'b']

    pipeline = discovery.load_pipeline('valid.pipeline')

    load_mock.assert_called_once_with('valid.pipeline', ['a', 'b'])

    assert pipeline == load_mock.return_value

def _get_pipeline_dict(pipeline, primitives):
        if isinstance(pipeline, dict):
            return pipeline

        elif isinstance(pipeline, str):
            return load_pipeline(pipeline)

        elif isinstance(pipeline, MLPipeline):
            return pipeline.to_dict()

        elif isinstance(pipeline, list):
            if primitives is not None:
                raise ValueError('if `pipeline` is a `list`, `primitives` must be `None`')

            return {'primitives': pipeline}

        elif pipeline is None:
            if primitives is None:
                raise ValueError('Either `pipeline` or `primitives` must be not `None`.')

            return dict()