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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 generateCertificate(self, alias, commonName, organizationalUnit, city, state, country, keyalg="RSA", keysize=1024, sigalg="SHA256withRSA", validity=90 ):
 """ Use this operation to create a self-signed certificate or as a starting point for getting a production-ready CA-signed certificate. The portal will generate a certificate for you and store it in its keystore. """

        params = {"f" : "json",
                  "alias" : alias,
                  "commonName" : commonName,
                  "organizationalUnit" : organizationalUnit,
                  "city" : city,
                  "state" : state,
                  "country" : country,
                  "keyalg" : keyalg,
                  "keysize" : keysize,
                  "sigalg" : sigalg,
                  "validity" : validity
                  }
        url = self._url + "/SSLCertificate/ generateCertificate"
        return self._post(url=url,
                          param_dict=params,
                          proxy_port=self._proxy_port,
                          proxy_url=self._proxy_url)