anchor.diff:  
   IRI_REF
       : '<' (~('<' | '>' | '"' | OPEN_CURLY_BRACE | CLOSE_CURLY_BRACE | PIPE | INVERSE | '`' | '\\' | '\u0000'..'\u0020'))* '>'
  -//    | LESS { $type = LESS; }
       ;
   
   PNAME_NS : PN_PREFIX? ':';
  
positive.code:     ;
      
  groupGraphPatternSub
      : triplesBlock?  groupGraphPatternSubList* //(f+=graphPatternNotTriples DOT? triplesBlock?)*
      ;
      
  groupGraphPatternSubList
  
negative.code:     ;
      
  triplesBlock
      : triplesSameSubjectPath (DOT triplesBlock?)?
      ;
  
  