internal static void GroupStart(this TokenStream stream)
 {
     stream.Add(new ExpressionToken(ExpressionTokenType.GroupStart, null));
 }
 internal static void Property(this TokenStream stream, string propertyName)
 {
     stream.Add(new ExpressionToken(ExpressionTokenType.Property, propertyName));
 }
 internal static void String(this TokenStream stream, string content)
 {
     stream.Add(new ExpressionToken(ExpressionTokenType.String, content));
 }
 internal static void Numeric(this TokenStream stream, int value)
 {
     stream.Add(new ExpressionToken(value));
 }
 internal static void Function(this TokenStream stream, string functionName)
 {
     stream.Add(new ExpressionToken(ExpressionTokenType.Element, functionName));
 }
 internal static void IndexEnd(this TokenStream stream)
 {
     stream.Add(new ExpressionToken(ExpressionTokenType.IndexEnd, null));
 }