code: public long getResponseAsFile(File f) throws HelloSignException {
          long bytesWritten = 0;
          try {
              bytesWritten = Files.copy(lastResponseStream, f.toPath(), StandardCopyOption.REPLACE_EXISTING);
          } catch (Exception e) {
              throw new HelloSignException(e);
          }
          return bytesWritten;
      }
docs: Write the last response to a file.
  
  @param f File
  @return long bytes written
  @throws HelloSignException Thrown if an exception occurs during the copy
  of the response stream to the given file.