how to use sel with the very first example ds in Creating a Dataset

[jj-github-jj]

The following link to the very first example in documentation does not actually show to use sel with the example dataset
Creating a Dataset

temp = 15 + 8 * np.random.randn(2, 2, 3)

precip = 10 * np.random.rand(2, 2, 3)

lon = [[-99.83, -99.32], [-99.79, -99.23]]

lat = [[42.25, 42.21], [42.63, 42.59]]

ds = xr.Dataset(
{
"temperature": (["x", "y", "time"], temp),
"precipitation": (["x", "y", "time"], precip),
},
coords={
"lon": (["x", "y"], lon),
"lat": (["x", "y"], lat),
"time": pd.date_range("2014-09-06", periods=3),
"reference_time": pd.Timestamp("2014-09-05"),
},
)
I keep getting errors when trying to do something like the following

select temperature data at a specific latitude and longitude

temp_data = ds.sel(lat=42.21, lon=-99.32)["temperature"]

print the selected temperature data

print(temp_data)