human
Solve the following python programming problem given the following code:
def query_class(QueryClass) : 
    '
    Returns a custom django.db.models.sql.query.Query subclass that is
    appropriate for MS SQL Server.
    ' 
    global _classes 
    try : 
        return _classes [_classes] 
except KeyError : 
        pass 
class PyOdbcSSQuery (QueryClass) : 
        from sql_server.pyodbc import aggregates 
        aggregates_module = aggregates 
        def __init__(self, * args, **kwargs) : 
            super (PyOdbcSSQuery, self).__init__ (* args, ** kwargs) 
            self.default_reverse_ordering = False 
            self._ord = [] 
            from django.db.models.sql.subqueries import InsertQuery 
            if isinstance (self, InsertQuery) : 
                self._orig_as_sql = self.as_sql 
                self.as_sql = self._insert_as_sql 
def _insert_as_sql(self, * args, **kwargs) : 
            "Helper method for monkeypatching Django InsertQuery's as_sql." 
            meta = self.get_meta () 
            quoted_table = self.connection.ops.quote_name (meta.db_table) 
            (sql, params) = self._orig_as_sql (* args, ** kwargs) 
            if (meta.has_auto_field and (meta.auto_field.column in self.columns)) : 
                if ((len (self.columns) == 1) and (not params)) : 
                    sql = ('INSERT INTO %s DEFAULT VALUES' % quoted_table) 
else : 
                    sql = ('SET IDENTITY_INSERT %s ON;
%s;
SET IDENTITY_INSERT %s OFF' % (quoted_table, sql, quoted_table)) 
return (sql, params) 
def __reduce__(self) : 
            "
            Enable pickling for this class (normal pickling handling doesn't
            work as Python can only pickle module-level classes by default).
            " 
            if hasattr (QueryClass, '__getstate__') : 
                assert hasattr (QueryClass, '__setstate__') 
                data = self.__getstate__ () 
else : 
                data = self.__dict__ 
return (unpickle_query_class, (QueryClass,), data) 
def convert_values(self, value, field) : 
            "
            Coerce the value returned by the...

    
    

    Fix the buggy line: return _classes [_classes]
assistant
#Here is Python program to fix the buggy line: return _classes [_classes]
.

return _classes [QueryClass]