anchor.diff:  WS : (' ' | '\t' | NL) -> skip;
   COMMENT: '/*' .*? '*/' -> skip;
   LINE_COMMENT : '//' ~[\r\n]* NL? -> skip;
  -STRING : '"' ('\\"' | ~'"')* '"';
  +DSTRING : '"' ('\\"' | ~'"')* '"';
  +SSTRING : '\'' ('\\\'' | ~'\'')* '\'';
   URL : 'url(' ~[)]* ')';
   COMMA : ',';
   SEMICOLON: ';';
  
positive.code:             
  value_list: value ( value )*;
  
  value : (VARIABLE | IDENTIFIER | STRING | integer ( DIMENSION | PERCENT)? );
  
  integer: (PLUS | MINUS)? DIGITS;
  
  
negative.code: ID_NAME: HASH IDENTIFIER;
  CLASS_NAME: DOT IDENTIFIER;
  
  string: DSTRING | SSTRING;
  
  import_target: URL | string;
  
  import_statement : IMPORT_KW
                     import_target ( ',' import_target )*
  