code: def next_builder(self):
          
          sequence = self.sequence + 1
          next_builder = Builder(
              horizon_uri=self.horizon.horizon_uri,
              address=self.address,
              network=self.network,
              sequence=sequence,
              fee=self.fee)
          next_builder.keypair = self.keypair
          return next_builder
docs: Create a new builder based off of this one with its sequence number
          incremented.
  
          :return: A new Builder instance
          :rtype: :class:`Builder`