def _setup(self):
        """
        sets up the SMIME.SMIME instance
        and loads the CA certificates store
        """
        smime = SMIME.SMIME()
        st = X509.X509_Store()
        if not os.access(self._certstore, os.R_OK):
            raise VerifierError, "cannot access %s" % self._certstore
        st.load_info(self._certstore)
        smime.set_x509_store(st)
        self._smime = smime

        sets up the SMIME.SMIME instance
        and loads the CA certificates store
        
recipes/Python/285211_verifying_SMIME_signed_email_M2Crypno_signers/recipe-285211.py