code: def deterministic(cls, mnemonic, passphrase='', lang='english', index=0):
          
          sm = StellarMnemonic(lang)
          seed = sm.to_seed(mnemonic, passphrase=passphrase, index=index)
          return cls.from_raw_seed(seed)
docs: Generate a :class:`Keypair` object via a deterministic
          phrase.
  
          Using a mnemonic, such as one generated from :class:`StellarMnemonic`,
          generate a new keypair deterministically. Uses :class:`StellarMnemonic`
          internally to generate the seed from the mnemonic, using PBKDF2.
  
          :param str mnemonic: A unique string used to deterministically generate
              keypairs.
          :param str passphrase: An optional passphrase used as part of the salt
              during PBKDF2 rounds when generating the seed from the mnemonic.
          :param str lang: The language of the mnemonic, defaults to english.
          :param int index: The index of the keypair generated by the mnemonic.
              This allows for multiple Keypairs to be derived from the same
              mnemonic, such as::
  
                  >>> from stellar_base.keypair import Keypair
                  >>> m = 'update hello cry airport drive chunk elite boat shaft sea describe number'  # Don't use this mnemonic in practice.
                  >>> kp1 = Keypair.deterministic(m, lang='english', index=0)
                  >>> kp2 = Keypair.deterministic(m, lang='english', index=1)
                  >>> kp3 = Keypair.deterministic(m, lang='english', index=2)
  
          :return: A new :class:`Keypair` instance derived from the mnemonic.