code: Rule Locrian() {
  		return Sequence(IgnoreCase("loc"),
  			Optional(Sequence(IgnoreCase("r"),
  				Optional(Sequence(IgnoreCase("i"),
  					Optional(Sequence(IgnoreCase("a"),
  						Optional(IgnoreCase("n"))
  					))
  				))
  			))
  		).label(Locrian).suppressSubnodes();
  	}
docs: minor with flat 2nd and 5th
  
  locrian ::= "loc" ["r" ["i" ["a" ["n"]]]]