Document where the cache fixture is used

tests/conftest.py

@@ -54,8 +54,10 @@ def pytest_addoption(parser):
 def cache(request: "FixtureRequest") -> CloudPickleCache:
     """Return a cache object that can persist state between testing sessions.
 
+    ```pycon
     cache.get(key, default)
     cache.set(key, value)
+    ```
 
     Keys must be ``/`` separated strings, where the first part is usually the
     name of your plugin or application to avoid clashes with other cache users.

tests/value/conftest.py

@@ -112,6 +112,8 @@ def analytic_banzhaf(dummy_utility):
 
 @pytest.fixture(scope="function")
 def linear_shapley(cache, linear_dataset, scorer, n_jobs):
+    """This fixture makes use of the cache fixture to avoid recomputing
+    exact shapley values for each test run."""
     args_hash = cache.hash_arguments(linear_dataset, scorer, n_jobs)
     u_cache_key = f"linear_shapley_u_{args_hash}"
     exact_values_cache_key = f"linear_shapley_exact_values_{args_hash}"