Answer
TypeError: '<' not supported between instances of 'tuple' and 'NoneType'
Work Step by Step
In the definition of min function there no return statement hence it return None type object. In the main function the statement min(min(5, 6), (51, 6)) will be reduced to min(None, (51, 6)) after calling the inner min function, then the outer min will be called which will try to compare both arguments one of which is None and other is a tuple and this comparison is invalid due to incompatible types, hence it will give TypeError
