human
Solve the following python programming problem given the following code:
def platform_validator(domain) : 
    'Validate if platform exists for given domain.' 
    def validator(value) : 
        'Test if platform exists.' 
        if (value is None) : 
            raise vol.Invalid ('platform cannot be None') 
if get_platform (domain, str (value)) : 
            return value 
raise vol.Invalid ('platform {} does not exist for {}'.format (value, domain)) 
return domain 

    
    

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

return def validator(