I think we need more tests for this mission;)

A lot of successful answers from many users are not correct here.

What about this example at 'Story'?

assert steps_to_convert('pline1', 'line2v') == 3

and so on...

assert steps_to_convert('get pline1 and more', 'get line2v and more') == 3

Try and you will see for yourself.