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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def no_witness(self):
        '''
        Tx -> bytes
        '''
        tx = bytes()
        tx += self.version
        tx += VarInt(len(self.tx_ins)).to_bytes()
        for tx_in in self.tx_ins:
            tx += tx_in.to_bytes()
        tx += VarInt(len(self.tx_outs)).to_bytes()
        for tx_out in self.tx_outs:
            tx += tx_out.to_bytes()
        tx += self.lock_time
        return bytes(tx)