I checked that the default value of the work sheet state isshow, but from my understanding the same holds true for the options object when adding worksheets since it's just passed down to the constructor (in this PR, it's default value isvisible). In that case, we should define this enum once and the re-use it in both type definitions. what do you think@Siemienik@guyonroche ?

@alubbe fully agree,

as far as i know, 'show' is invalid value, it should be 'visible'
#621