public bool Equals(CssSpecificity other)
 {
     if (ReferenceEquals(null, other)) return false;
     if (ReferenceEquals(this, other)) return true;
     return Equals(other._data, _data);
 }
 internal void Subtract(CssSpecificity specificity)
 {
     _data[0] -= specificity._data[0];
     _data[1] -= specificity._data[1];
     _data[2] -= specificity._data[2];
     _data[3] -= specificity._data[3];
 }
 public static CssSpecificity Sum(this IEnumerable<CssSpecificity> collection)
 {
     var result = new CssSpecificity();
     foreach (var specificity in collection)
         result.Add(specificity);
     return result;
 }
 internal void Add(CssSpecificity specificity)
 {
     _data[0] += specificity._data[0];
     _data[1] += specificity._data[1];
     _data[2] += specificity._data[2];
     _data[3] += specificity._data[3];
 }