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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def isRecord(self, db=None):
 """ Returns whether or not this database table record exists in the database. :return <bool> """

        if db is not None:
            same_db = db == self.context().db

        if db is None or same_db:
            col = self.schema().idColumn()
            with ReadLocker(self.__dataLock):
                return (col in self.__loaded) and (self.__values[col.name()][0] is not None)
        else:
            return None