How to use the whisper.diff function in whisper

def test_diff(self):
        testdb = "test-%s" % self.filename

        now = int(time.time())

        self.addCleanup(self._remove, testdb)
        whisper.create(testdb, self.retention)

        whisper.create(self.filename, self.retention)

        whisper.update(testdb, 1.0, now)
        whisper.update(self.filename, 2.0, now)

        results = whisper.diff(testdb, self.filename)

        expected = [(0, [(int(now), 1.0, 2.0)], 1), (1, [], 0)]

        self.assertEqual(results, expected)

now = time.time()

        self.addCleanup(self._remove, testdb)
        whisper.create(testdb, self.retention)

        whisper.create(self.filename, self.retention)

        whisper.update(testdb, 1.0, now)
        whisper.update(self.filename, 2.0, now)

        # Purposefully insert nulls to strip out
        previous = now - self.retention[0][0]
        whisper.update(testdb, float('NaN'), previous)

        results = whisper.diff(testdb, self.filename, ignore_empty=True)
        self.assertEqual(
            results,
            [(0, [(int(now), 1.0, 2.0)], 1), (1, [], 0)],
        )

        results_empties = whisper.diff(testdb, self.filename, ignore_empty=False)
        expected = [(0, [(int(previous), float('NaN'), None), (int(now), 1.0, 2.0)], 2), (1, [], 0)]

        # Stupidly, float('NaN') != float('NaN'), so assert that the
        # repr() results are the same :/
        #
        # See this thread:
        #    https://mail.python.org/pipermail/python-ideas/2010-March/006945.html
        self.assertEqual(
            repr(results_empties),
            repr(expected),

whisper.create(self.filename, self.retention)

        whisper.update(testdb, 1.0, now)
        whisper.update(self.filename, 2.0, now)

        # Purposefully insert nulls to strip out
        previous = now - self.retention[0][0]
        whisper.update(testdb, float('NaN'), previous)

        results = whisper.diff(testdb, self.filename, ignore_empty=True)
        self.assertEqual(
            results,
            [(0, [(int(now), 1.0, 2.0)], 1), (1, [], 0)],
        )

        results_empties = whisper.diff(testdb, self.filename, ignore_empty=False)
        expected = [(0, [(int(previous), float('NaN'), None), (int(now), 1.0, 2.0)], 2), (1, [], 0)]

        # Stupidly, float('NaN') != float('NaN'), so assert that the
        # repr() results are the same :/
        #
        # See this thread:
        #    https://mail.python.org/pipermail/python-ideas/2010-March/006945.html
        self.assertEqual(
            repr(results_empties),
            repr(expected),
        )
        # Since the above test is somewhat of a sham, ensure that there
        # is a nan where there should be.
        self.assertTrue(
            math.isnan(results_empties[0][1][0][1])
        )

def main():
  archive_diffs = whisper.diff(path_a, path_b, ignore_empty=options.ignore_empty,
                               until_time=until_time)
  if options.summary:
    if options.json:
      print_summary_json(archive_diffs, path_a, path_b)
    else:
      print_summary(archive_diffs, pretty=(not options.columns),
                    headers=(not options.no_headers))
  else:
    if options.json:
      print_diffs_json(archive_diffs, path_a, path_b)
    else:
      print_diffs(archive_diffs, pretty=(not options.columns),
                  headers=(not options.no_headers))