human
Solve the following python programming problem given the following code:
@ check.implementation (* aggregations) 
def Aggregation_check(aggregation) : 
    aggregation.errors = [] 
    def error(message) : 
        aggregation.errors.append (message) 
allowed_specifications = (To, From, Months) 
    specification_errors = False 
    if (not isinstance (aggregation.dataset_name, str)) : 
        error ('First argument should be the name of a data set enclosed in parentheses. ') 
else : 
        if SampleTable.name_exists (aggregation.dataset_name, error) : 
            aggregation.sample_table = SampleTable.with_name (aggregation.dataset_name) 
for specification in aggregation.specification : 
        if (not isinstance (specification, allowed_specifications)) : 
            error (('%(specification)s cannot be used inside %(aggregation_name)s(...).
Required arguments are table name: %(table_names)s.
Optional arguments are %(possibilities)s.' % dict (specification = specification, aggregation_name = aggregation.__class__.__name__, table_names = ', '.join (map ('"%s %s"'.__mod__, climate_sample_tables)), possibilities = ', '.join (((Class.__name__ + '(...)') for Class in <MASK>))))) 
specification_errors |= bool (check (specification)) 
return (aggregation.errors or specification_errors) 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: Class, specification, allowed_specifications, specification_errors, error, aggregation
assistant
#Here is a proper replacement for <MASK>.
allowed_specifications