How to use the cfgrib.dataset function in cfgrib

def test_dict_merge():
    master = {'one': 1}
    dataset.dict_merge(master, {'two': 2})
    assert master == {'one': 1, 'two': 2}
    dataset.dict_merge(master, {'two': 2})
    assert master == {'one': 1, 'two': 2}

    with pytest.raises(dataset.DatasetBuildError):
        dataset.dict_merge(master, {'two': 3})

def test_enforce_unique_attributes():
    assert dataset.enforce_unique_attributes({'key': [1]}, ['key'])
    assert not dataset.enforce_unique_attributes({'key': ['undef']}, ['key'])

    with pytest.raises(dataset.DatasetBuildError):
        assert dataset.enforce_unique_attributes({'key': [1, 2]}, ['key'])

def merge_grib_keys(grib_keys, detected_grib_keys, default_grib_keys):
    merged_grib_keys = {k: v for k, v in grib_keys.items()}
    dataset.dict_merge(merged_grib_keys, detected_grib_keys)
    for key, value in default_grib_keys.items():
        if key not in merged_grib_keys:
            merged_grib_keys[key] = value
    return merged_grib_keys

def expand_dims(data_var):
    coords_names = []
    for coord_name in dataset.ALL_HEADER_DIMS + ALL_TYPE_OF_LEVELS:
        if coord_name in data_var.coords and data_var.coords[coord_name].size == 1:
            data_var = data_var.expand_dims(coord_name)
        if coord_name in data_var.dims:
            coords_names.append(coord_name)
    return coords_names, data_var