code: private void encodeThis() throws IOException {
          if (keyUsages == null || keyUsages.isEmpty()) {
              this.extensionValue = null;
              return;
          }
          DerOutputStream os = new DerOutputStream();
          DerOutputStream tmp = new DerOutputStream();
  
          for (int i = 0; i < keyUsages.size(); i++) {
              tmp.putOID(keyUsages.elementAt(i));
          }
  
          os.write(DerValue.tag_Sequence, tmp);
          this.extensionValue = os.toByteArray();
      }
docs: Encode this extension value.