anchor.diff:  
   subscript
       : ELLIPSIS
  -    | test
  -    | test? COLON test? sliceop?
  +    | test (COLON test? sliceop?)?
  +    | COLON test? sliceop?
       ;
   
   // TODO: maybe inline?
  
positive.code:     ;
  
  assign_part
      : (ASSIGN testlist_star_expr)+ | (ASSIGN testlist_star_expr)* ASSIGN yield_expr // if left expression in assign is bool literal, it's mean that is Python 2 here
      | COLON test (ASSIGN testlist)? // annassign Python3 rule
      | op=( ADD_ASSIGN
           | SUB_ASSIGN
           | MULT_ASSIGN
  
negative.code:  */
  parser grammar PythonParser;
  
  options { tokenVocab=PythonLexer; superClass=PythonBaseParser; }
  
  root
      : (single_input
  