code: function foundNestedPseudoClass() {
              var openParen = 0;
              for (var i = pos + 1; i < source_text.length; i++) {
                  var ch = source_text.charAt(i);
                  if (ch === "{") {
                      return true;
                  } else if (ch === '(') {
                      // pseudoclasses can contain ()
                      openParen += 1;
                  } else if (ch === ')') {
                      if (openParen === 0) {
                          return false;
                      }
                      openParen -= 1;
                  } else if (ch === ";" || ch === "}") {
                      return false;
                  }
              }
              return false;
          }
docs: Nested pseudo-class if we are insideRule and the next special character found opens a new block