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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 is_user_valid(self, userID):
 """ Check if this User ID is valid. """

        cur = self.conn.cursor()
        cur.execute('SELECT * FROM users WHERE id=? LIMIT 1', [userID])
        results = cur.fetchall()
        cur.close()
        return len(results) > 0