code: public static UploadAttachmentResponse postUploadAttachment(
  			StringEntity input) {
  		String pageToken = FbBotMillContext.getInstance().getPageToken();
  		// If the page token is invalid, returns.
  		if (!validatePageToken(pageToken)) {
  			return null;
  		}
  
  		String url = FbBotMillNetworkConstants.FACEBOOK_BASE_URL
  				+ FbBotMillNetworkConstants.FACEBOOK_UPLOAD_API_URL + pageToken;
  		BotMillNetworkResponse response = postInternal(url, input);
  
  		// Parses the response as a UploadAttachmentResponse and returns it.
  		return FbBotMillJsonUtils.fromJson(response.getResponse(),
  				UploadAttachmentResponse.class);
  	}
docs: POSTs an attachment as a JSON string to Facebook.
  
  @param input
  the JSON data to send.
  @return the uploaded attachment ID.