code: private static boolean isSelector( StringBuilder builder ) {
          int length = builder.length();
          if( length == 0 ) {
              return false;
          }
          switch( builder.charAt( 0 ) ) { 
              case '.': // Mixin
              case '#': // Mixin
                  break;
              default:
                  return true;
          }
          for( int i = 1; i < length; i++ ) {
              char ch = builder.charAt( i );
              switch( ch ) {
                  case '>':
                  case ':':
                      return true;
              }
          }
          return false;
      }
docs: If the builder contains a selector and not a mixin.
  @param builder the builder
  @return true, if it 100% a selector and not a mixin with parameters