def Start(self):
    """Starts the profiler."""
    filename = '{0:s}-{1:s}.csv.gz'.format(
        self._FILENAME_PREFIX, self._identifier)
    if self._path:
      filename = os.path.join(self._path, filename)

    self._sample_file = gzip.open(filename, 'wb')
    self._WritesString(self._FILE_HEADER)

    self._start_time = time.time()
Starts the profiler.