STY: Apply ruff/flake8-simplify rule SIM401

SIM401 Use `.get()` instead of an `if` block

nipype/interfaces/io.py

@@ -2942,7 +2942,7 @@ def __init__(self, infields=None, **kwargs):
         undefined_traits = {}
         for key in self._infields:
             self.inputs.add_trait(key, traits.Any)
-            undefined_traits[key] = kwargs[key] if key in kwargs else Undefined
+            undefined_traits[key] = kwargs.get(key, Undefined)
 
         self.inputs.trait_set(trait_change_notify=False, **undefined_traits)