code: def test_scale_colors_for_png(self, arr, vmin, vmax, expected):
      arr = np.array(arr)
      scaled = vis.scale_colors_for_png(arr, vmin=vmin, vmax=vmax)
      self.assertTrue((scaled == expected).all())
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import glob
  import os
  from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.testing import test_utils
  from third_party.nucleus.util import vis
  from tensorflow.core.example import example_pb2
  from tensorflow.core.example import feature_pb2
label_desc: Use image node_id 7 for calling the VisTest obj's underlying member method code with example usage: obj.test_scale_colors_for_png(arr, vmin, vmax, expected) without return types