code: protected void upload(final String text, final ProgressListener progressListener, ResponseListener responseListener) {
          if (text == null || text.length() == 0) {
              if (responseListener != null) {
                  responseListener.onFailure(null, new IllegalArgumentException("Tried to upload empty text"), null);
              }
              return;
          }
  
          String contentTypeHeader = headers.get(CONTENT_TYPE);
          final String contentType = contentTypeHeader != null ? contentTypeHeader : TEXT_PLAIN_CONTENT_TYPE;
  
          RequestBody body = RequestBody.create(MediaType.parse(contentType), text);
  
  
          // Custom RequestBody wrapper that monitors the progress of the upload
  
          ProgressRequestBody progressBody = new ProgressRequestBody(text, body, progressListener);
  
          sendRequest(null, responseListener, progressBody);
      }
docs: Upload text asynchronously.
  If the Content-Type header was not previously set, this method will set it to "text/plain".
  
  @param text              The text to upload
  @param progressListener  The listener that monitors the upload progress
  @param responseListener  The listener whose onSuccess or onFailure methods will be called when this request finishes