@Override
    public String toString() {
        StringBuilder bld = new StringBuilder();
        if (sessionId == INVALID_SESSION_ID) {
            bld.append("(sessionId=INVALID, ");
        } else {
            bld.append("(sessionId=").append(sessionId).append(", ");
        }
        if (epoch == INITIAL_EPOCH) {
            bld.append("epoch=INITIAL)");
        } else if (epoch == FINAL_EPOCH) {
            bld.append("epoch=FINAL)");
        } else {
            bld.append("epoch=").append(epoch).append(")");
        }
        return bld.toString();
    }
Return the metadata for the next incremental response.
clients/src/main/java/org/apache/kafka/common/requests/FetchMetadata.java