Writes the frame to disk as a tensor summary.

def _write_summary(self, session, frame):
    '''Writes the frame to disk as a tensor summary.'''
    summary = session.run(self.summary_op, feed_dict={
        self.frame_placeholder: frame
    })
    path = '{}/{}'.format(self.PLUGIN_LOGDIR, SUMMARY_FILENAME)
    write_file(summary, path)