code: public void startPart(String contentType, String[] headers) throws IOException {
          if (inPart)
              out.write(__CRLF);
          out.write(__DASHDASH);
          out.write(boundary);
          out.write(__CRLF);
          out.write("Content-Type: ");
          out.write(contentType);
          out.write(__CRLF);
          for (int i = 0; headers != null && i < headers.length; i++) {
              out.write(headers[i]);
              out.write(__CRLF);
          }
          out.write(__CRLF);
          inPart = true;
      }
docs: Start creation of the next Content.
  
  @param contentType the content type of the part
  @param headers     the part headers
  @throws IOException if unable to write the part