code: def use_tsig(self, keyring, keyname=None,
                   algorithm=dns.tsig.default_algorithm):
          
          self.keyring = keyring
          if keyname is None:
              self.keyname = self.keyring.keys()[0]
          else:
              self.keyname = keyname
          self.keyalgorithm = algorithm
docs: Add a TSIG signature to the query.
  
          @param keyring: The TSIG keyring to use; defaults to None.
          @type keyring: dict
          @param keyname: The name of the TSIG key to use; defaults to None.
          The key must be defined in the keyring.  If a keyring is specified
          but a keyname is not, then the key used will be the first key in the
          keyring.  Note that the order of keys in a dictionary is not defined,
          so applications should supply a keyname when a keyring is used, unless
          they know the keyring contains only one key.
          @param algorithm: The TSIG key algorithm to use.  The default
          is dns.tsig.default_algorithm.
          @type algorithm: string