String removePendingDocCommentLines() {
        if (docCommentLines.isEmpty()) {
            return null;
        } else {
            StringBuilder result = new StringBuilder();
            while (!docCommentLines.isEmpty()) {
                result.append(docCommentLines.removeFirst()).append("\n");
            }
            // Strip ending \n.
            result.setLength(result.length() - 1);
            return result.toString();
        }
    }
Removes any buffered documentation comment lines, and returns a concatenated string value.

@return Returns the combined documentation comment string for the given lines. Returns null if no lines.
smithy-model/src/main/java/software/amazon/smithy/model/loader/IdlInternalTokenizer.java