code: private ParseTree parseEquality(Expression expressionIn) {
      SourcePosition start = getTreeStartLocation();
      ParseTree left = parseRelational(expressionIn);
      while (peekEqualityOperator()) {
        Token operator = nextToken();
        ParseTree right = parseRelational(expressionIn);
        left = new BinaryOperatorTree(getTreeLocation(start), left, operator, right);
      }
      return left;
    }
docs: 11.9 Equality Expression