text: const { Transform } = require('stream');
  
  class AppendInitVect extends Transform {
    constructor(initVect, opts) {
      super(opts);
      this.initVect = initVect;
      this.appended = false;
    }
  
    _transform(chunk, encoding, cb) {
      if (!this.appended) {
        this.push(this.initVect);
        this.appended = true;
      }
      this.push(chunk);
      cb();
    }
  }
  
  module.exports = AppendInitVect;