code: def test_format_time(self):
      self.assertEqual("01:06:40", format_time(4000))
      self.assertEqual("02:05", format_time(125))
      self.assertEqual("45 sec", format_time(45))
      self.assertEqual("100 ms", format_time(0.1))
      self.assertEqual("10 μs", format_time(1e-5))
      self.assertEqual("200 ns", format_time(2e-7))
  
imports: from __future__ import unicode_literals
  from collections import namedtuple
  import numpy
  import progressbar
  from sklearn.datasets import make_classification
  from neupy import algorithms, layers
  from neupy.exceptions import StopTraining
  from neupy.algorithms.signals import format_time
  from base import BaseTestCase
  from helpers import catch_stdout
label_desc: Use image node_id 7 for calling the SignalsTestCase obj's underlying member method code with example usage: obj.test_format_time() without return types