I have written the following snippet for UltiSnips in Vim. With this snippet I want to add an apostrophe to all lilypond pitches:

snippet 1 "lilypond pitches with apostophes"
$1
${1/w+s*/$0'/g}
endsnippet

When I execute it, however, the text appears twice:

c d e
c' d' e'

I just want the 2nd line

I’ve tried snippet 1 “lilypond pitches with apostophes”

snippet 1
${1/w+s*/$0'/g}
endsnippet

but this gives an error:

UltiSnips Error:

Tabstop 1 is not known but is used by a Transformation