code: Rule Ionian() {
  		return Sequence(IgnoreCase("ion"),
  			Optional(Sequence(IgnoreCase("i"),
  				Optional(Sequence(IgnoreCase("a"),
  					Optional(IgnoreCase("n"))
  				))
  			))
  		).label(Ionian).suppressSubnodes();
  	}
docs: =major
  
  ionian ::= "ion" ["i" ["a" ["n"]]]