code: @ObjectiveCName("sendDocumentWithPeer:withName:withMime:withDescriptor:")
      public void sendDocument(Peer peer, String fileName, String mimeType, String descriptor) {
          sendDocument(peer, fileName, mimeType, null, descriptor);
      }
docs: Send document without preview
  
  @param peer       destination peer
  @param fileName   File name (without path)
  @param mimeType   mimetype of document
  @param descriptor File Descriptor