code: def encrypt_assertion(self, statement, enc_key, template, key_type='des-192', node_xpath=None):
          
          return self.crypto.encrypt_assertion(
                  statement, enc_key, template, key_type, node_xpath)
docs: Will encrypt an assertion
  
          :param statement: A XML document that contains the assertion to encrypt
          :param enc_key: File name of a file containing the encryption key
          :param template: A template for the encryption part to be added.
          :param key_type: The type of session key to use.
          :return: The encrypted text