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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 lookup(self, public_key):
 """ Look up certificate by public key, returns zcert_t object if found, else returns NULL. The public key is provided in Z85 text format. """

        return Zcert(lib.zcertstore_lookup(self._as_parameter_, public_key), False)