This prints the text from 1% to 100%, all on the same line since it uses stdout.write rather than print. However, before printing each percentage it first prints \u001b[1000D, which means "move cursor left by 1000 characters). This should move it all the way to the left of the screen, thus letting the new percentage that gets printed over-write the old one. Hence we see the loading percentage seamlessly changing from 1% to 100% before the function returns:
第一百六十七条 起拖前，因不可抗力或者其他不能归责于双方的原因致使合同不能履行的，双方均可以解除合同，并互相不承担赔偿责任。除合同另有约定外，拖航费已经支付的，承拖方应当退还给被拖方。
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Common subexpression elimination
it is worth optimising.