code: @Override
      public void startedPart(Map headers) {
          if (_docReader != null)
              throw new IllegalStateException("_docReader is already defined");
          Log.v(TAG, "%s: Starting new document; headers =%s", this, headers);
          _docReader = new MultipartDocumentReader(db);
          _docReader.setHeaders(headers);
          _docReader.startedPart(headers);
      }
docs: This method is called when a part's headers have been parsed, before its data is parsed.