Define identity processing function

audinterface/core/process.py

@@ -157,9 +157,7 @@ def __init__(
             channels = audeer.to_list(channels)
 
         if process_func is None:
-
-            def process_func(signal, _):
-                return signal
+            process_func = utils.identity
 
         if resample and sampling_rate is None:
             raise ValueError("sampling_rate has to be provided for resample = True.")

audinterface/core/utils.py

@@ -52,6 +52,11 @@ def assert_index(obj: pd.Index):
         audformat.assert_index(obj)
 
 
+def identity(signal, sampling_rate):
+    """Identity processing function."""
+    return signal
+
+
 def is_scalar(value: typing.Any) -> bool:
     r"""Check if value is scalar."""
     return (value is not None) and (