Format python files with black

diff --git a/compiler/back_end/cpp/BUILD b/compiler/back_end/cpp/BUILD
index 950298d..6bd9e39 100644
--- a/compiler/back_end/cpp/BUILD
+++ b/compiler/back_end/cpp/BUILD

@@ -547,7 +547,6 @@
 cpp_golden_test(
     name = "no_enum_traits_golden_test",
     emb_file = "//testdata:no_enum_traits.emb",
-    extra_args = ["--no-cc-enum-traits"],
     golden_file = "//testdata/golden_cpp:no_enum_traits.emb.h",
 )
 

diff --git a/compiler/back_end/cpp/build_defs.bzl b/compiler/back_end/cpp/build_defs.bzl
index 9208363..087dfca 100644
--- a/compiler/back_end/cpp/build_defs.bzl
+++ b/compiler/back_end/cpp/build_defs.bzl

@@ -47,7 +47,7 @@
         **kwargs
     )
 
-def cpp_golden_test(name, emb_file, golden_file, import_dirs = [], extra_args = []):
+def cpp_golden_test(name, emb_file, golden_file, import_dirs = []):
     """Defines a C++ golden file test.
 
     Args:
@@ -55,7 +55,6 @@
         emb_file: The .emb file to test.
         golden_file: The golden .h file.
         import_dirs: A list of import directories.
-        extra_args: A list of extra arguments to pass to the compiler.
     """
     py_test(
         name = name,
@@ -67,7 +66,7 @@
             "$(location :emboss_codegen_cpp)",
             "$(location %s)" % emb_file,
             "$(location %s)" % golden_file,
-        ] + ["--import-dir=" + d for d in import_dirs] + extra_args,
+        ] + ["--import-dir=" + d for d in import_dirs],
         data = [
             "//compiler/front_end:emboss_front_end",
             ":emboss_codegen_cpp",

diff --git a/compiler/back_end/cpp/header_generator.py b/compiler/back_end/cpp/header_generator.py
index 61e1ff7..c8df290 100644
--- a/compiler/back_end/cpp/header_generator.py
+++ b/compiler/back_end/cpp/header_generator.py

@@ -1462,7 +1462,12 @@
             ).rendered
             key = "SWITCH:" + discrim_str
             if key not in groups:
-                groups[key] = {"type": "switch", "expr": discrim_expr, "cases": [], "seen_cases": set()}
+                groups[key] = {
+                    "type": "switch",
+                    "expr": discrim_expr,
+                    "cases": [],
+                    "seen_cases": set(),
+                }
                 ordered_keys.append(key)
 
             case_str = _render_case_label(case_expr, ir)