human
Solve the following python programming problem given the following code:
def key_dependency(key, dependency) : 
    'Validate that all dependencies exist for key.' 
    def validator(value) : 
        'Test dependencies.' 
        if (not isinstance (value, dict)) : 
            raise vol.Invalid ('key dependencies require a dict') 
if ((key in value) and (dependency not in value)) : 
            raise vol.Invalid ('dependency violation - key "{}" requires key "{}" to exist'.format (key, dependency)) 
return value 
return dependency 

    
    

    Fix the buggy line: return dependency
assistant
#Here is Python program to fix the buggy line: return dependency
.

return def validator(