code: Rule Phrygian() {
  		return Sequence(IgnoreCase("phr"),
  			Optional(Sequence(IgnoreCase("y"),
  				Optional(Sequence(IgnoreCase("g"),
  					Optional(Sequence(IgnoreCase("i"),
  						Optional(Sequence(IgnoreCase("a"),
  								Optional(IgnoreCase("n"))
  						))
  					))
  				))
  			))
  		).label(Phrygian).suppressSubnodes();
  	}
docs: minor with flat 2nd
  
  phrygian ::= "phr" ["y" ["g" ["i" ["a" ["n"]]]]]