diff --git a/cppwg/utils/utils.py b/cppwg/utils/utils.py
index 4232a6a..1a6e379 100644
--- a/cppwg/utils/utils.py
+++ b/cppwg/utils/utils.py
@@ -172,7 +172,7 @@ def read_source_file(
     return source
 
 
-def str_to_num(expr: str, integer:bool = False) -> Number:
+def str_to_num(expr: str, integer: bool = False) -> Number:
     """
     Convert a literal string expression to a number e.g. "(-1)" to -1.
 
diff --git a/cppwg/writers/constructor_writer.py b/cppwg/writers/constructor_writer.py
index 6fa47a4..e1cb032 100644
--- a/cppwg/writers/constructor_writer.py
+++ b/cppwg/writers/constructor_writer.py
@@ -188,7 +188,9 @@ def generate_wrapper(self) -> str:
             ):
                 # Try to convert "(-1)" to "-1" etc.
                 default_value = str(arg.default_value)
-                value = utils.str_to_num(default_value, integer="int" in str(arg.decl_type))
+                value = utils.str_to_num(
+                    default_value, integer="int" in str(arg.decl_type)
+                )
                 if value is not None:
                     default_value = str(value)
 
diff --git a/cppwg/writers/free_function_writer.py b/cppwg/writers/free_function_writer.py
index 5c77bb9..1681110 100644
--- a/cppwg/writers/free_function_writer.py
+++ b/cppwg/writers/free_function_writer.py
@@ -54,7 +54,9 @@ def generate_wrapper(self) -> str:
                 if arg.default_value is not None:
                     # Try to convert "(-1)" to "-1" etc.
                     default_value = str(arg.default_value)
-                    value = utils.str_to_num(default_value, integer="int" in str(arg.decl_type))
+                    value = utils.str_to_num(
+                        default_value, integer="int" in str(arg.decl_type)
+                    )
                     if value is not None:
                         default_value = str(value)
                     default_args += f" = {default_value}"
diff --git a/cppwg/writers/method_writer.py b/cppwg/writers/method_writer.py
index c91cf68..07cd99b 100644
--- a/cppwg/writers/method_writer.py
+++ b/cppwg/writers/method_writer.py
@@ -158,7 +158,9 @@ def generate_wrapper(self) -> str:
             ):
                 # Try to convert "(-1)" to "-1" etc.
                 default_value = str(arg.default_value)
-                value = utils.str_to_num(default_value, integer="int" in str(arg.decl_type))
+                value = utils.str_to_num(
+                    default_value, integer="int" in str(arg.decl_type)
+                )
                 if value is not None:
                     default_value = str(value)