code: def gen_tx(self):
          
          if not self.address:
              raise StellarAddressInvalidError('Transaction does not have any source address.')
          if self.sequence is None:
              raise SequenceError('No sequence is present, maybe not funded?')
          tx = Transaction(
              source=self.address,
              sequence=self.sequence,
              time_bounds=self.time_bounds,
              memo=self.memo,
              fee=self.fee * len(self.ops),
              operations=self.ops)
          self.tx = tx
          return tx
docs: Generate a :class:`Transaction
          <stellar_base.transaction.Transaction>` object from the list of
          operations contained within this object.
  
          :return: A transaction representing all of the operations that have
              been appended to this builder.
          :rtype: :class:`Transaction <stellar_base.transaction.Transaction>`