Apply suggestions from code review of branch dont-mutate-tuning-files

Co-authored-by: Joe Knapper <joe.knapper@glasgow.ac.uk>

hardware-specific-tests/picamera2/cam_test_utils/__init__.py

@@ -17,11 +17,11 @@ def camera_test_client(
 ):
     """Yield a camera ThingClient on a camera server.
 
-    This is a context manager not a pytest fixture as it needs to be created
+    This is a context manager, not a pytest fixture, as it needs to be created
     multiple times in some tests.
 
     :param cam: The camera Thing to be used. If not supplied a new one will be created.
-    :param settings_folder: The settings folder for the camera, if none is supplies new
+    :param settings_folder: The settings folder for the camera, if none is supplied, new
         temporary directory will be used as the settings folder.
     """
     if cam is None:

src/openflexure_microscope_server/things/camera/picamera_tuning_file_utils.py

@@ -36,14 +36,21 @@ def find_tuning_algo(tuning: dict[str, dict], name: str) -> dict[str, Any]:
     it can be tested independently of installing picamera2
 
     :param tuning: The camera tuning dictionary
-    :param name: The name of the algorithm
+    :param name: The key for the algorithm in the tuning file
     :return: The algorithm from the tuning dictionary. Editing this will edit the
         original dictionary.
     """
     version = tuning.get("version", 1)
+    # Version 1 of the tuning files was simply a dictionary of algorithms. Later
+    # versions have an "algorithms" key, the value of which is a list of algorithms.
     if version == 1:
         return tuning[name]
-    return next(algo for algo in tuning["algorithms"] if name in algo)[name]
+    # The tuning file "algorithms" is a list of dictionaries
+    algorithms = tuning["algorithms"]
+    # The list is a list of dictionaries that have 1 key: the algorithm name
+    algo_dict = next(algo for algo in algorithms if name in algo)
+    # We want the value for that key, which is a dictionary of algorithm parameters
+    return algo_dict[name]
 
 
 def set_static_lst(
@@ -136,8 +143,8 @@ def set_ce_to_disabled(
 ) -> dict:
     """Set ``ce_enable`` in ``rpi.contrast`` to zero to disable adaptive contrast enhancement.
 
-    :param tuning: The raspberry pi tuning file.
-    :returns: A deepcopu of the input file set ce_enable to 0.
+    :param tuning: The raspberry pi camera tuning file.
+    :returns: A deepcopy of the input file with ce_enable set to 0.
     """
     output_tuning = deepcopy(tuning)
     contrast = find_tuning_algo(output_tuning, "rpi.contrast")