anchor.diff:    }
   
     Python3Lexer.prototype.atStartOfInput = function() {
  -    return false;
  +    return this.getCharIndex() === 0;
     }
   }
   
  
positive.code:   let CommonToken = require('antlr4/Token').CommonToken;
    let Python3Parser = require('./Python3Parser').Python3Parser;
  
    // A queue where extra tokens are pushed on (see the NEWLINE lexer rule).
    Python3Lexer.prototype.tokens = [];
  
    // The stack that keeps track of the indentation level.
    Python3Lexer.prototype.indents = [];
  
    // The amount of opened braces, brackets and parenthesis.
    Python3Lexer.prototype.opened = 0;
  
    // The most recently produced token.
    Python3Lexer.prototype.lastToken = null;
  
    Python3Lexer.prototype.emit = function(t) {
      if (typeof t === 'undefined') {
        return antlr4.Lexer.prototype.emit.call(this);
      }
  
      this._token = t;
      this.tokens.push(t);
    };
  
    /**
  
negative.code:        if (indent === previous) {
           // skip indents of the same size as the present indent-size
           this.skip();
         } else if (indent > previous) {
           this.indents.push(indent);
           this.emitToken(this.commonToken(Python3Parser.INDENT, spaces));
         } else {
           // Possibly emit more than 1 DEDENT token.
           while (this.indents.length && this.indents[this.indents.length - 1] > indent) {
             this.emitToken(this.createDedent());
             this.indents.pop();
           }
         }
  