<S> = colour <whitespace some-bags whitespace 'contain' whitespace> ((quantity (<whitespace some-bags ', '> quantity)*) | <'no other'>) <whitespace some-bags '.'>
quantity = number <whitespace> colour
colour = word <whitespace> word
<word> = #'[a-z]+'
some-bags = 'bag' 's'?
<whitespace> = #'\s+'
<number> = #'[0-9]+'
