human
Solve the following python programming problem given the following code:
def _tests_by_properties(self, tests_to_targets, * properties) : 
    def combined_property(target) : 
        return tuple ((prop (target) for prop in properties)) 
return self._tests_by_property (tests_to_targets, <MASK>) 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: properties, tests_to_targets, self
assistant
#Here is a proper replacement for <MASK>.
def combined_property(