refactor: return NotImplemented instead of raising NotImplementedError

Special methods corresponding to numeric operators, rich comparison operators, and the `__length_hint__` method should return `NotImplemented` when the operation is not supported. These methods should not raise `NotImplementedError` as callers don't expect it and won't catch this exception.

Author: deepsource-dev-autofix[bot]

return_not_implemented.py

@@ -5,7 +5,7 @@ def __init__(self, val):
         self.val = val
 
     def __add__(self, other):
-        raise NotImplementedError
+        return NotImplemented
 
 
 class ComplexNumber: