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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 einfo(self, db=None):
 """query the einfo endpoint :param db: string (optional) :rtype: EInfo or EInfoDB object If db is None, the reply is a list of databases, which is returned in an EInfo object (which has a databases() method). If db is not None, the reply is information about the specified database, which is returned in an EInfoDB object. (Version 2.0 data is automatically requested.) """


        if db is None:
            return EInfoResult(self._qs.einfo()).dblist
        return EInfoResult(self._qs.einfo({'db': db, 'version': '2.0'})).dbinfo