anchor.diff:  class Filter {
   
     int _filterType;
  -
     int get filterType => _filterType;
   
     // The assertion value for this filter.
  
positive.code:   Filter(this._filterType, [this._attributeName, this._assertionValue, this._subFilters]);
  
    static Filter equals(String attributeName, String attrValue) => new Filter(TYPE_EQUALITY, attributeName, attrValue);
  
  
    static Filter and(List<Filter> filters) => new Filter(TYPE_AND, null, null, filters);
  
  
    static Filter or(List<Filter> filters) => new Filter(TYPE_OR, null, null, filters);
  
  
    static Filter not(Filter f) => new Filter(TYPE_NOT, null, null, [f]);
  
    static Filter present(String attrName) => new Filter(TYPE_PRESENCE, attrName);
  
  
  
negative.code: 
    Filter operator &(Filter other) => Filter.and([this, other]);
    Filter operator |(Filter other) => Filter.or([this, other]);
   
    String toString() => "Filter(type=$_filterType attrName=$_attributeName val=$_assertionValue, subFilters=$_subFilters)";
  
    /**
  