code: def assert_null_scaling(self, arr, slope, inter):
      # Assert scaling makes no difference to img, load, save
      img_class = self.image_class
      input_hdr = img_class.header_class()
      # Scaling makes no difference to array returned from get_data
      self._set_raw_scaling(input_hdr, slope, inter)
      img = img_class(arr, np.eye(4), input_hdr)
      img_hdr = img.header
      self._set_raw_scaling(input_hdr, slope, inter)
      assert_array_equal(img.get_fdata(), arr)
      # Scaling has no effect on image as written via header (with rescaling
      # turned off).
      fm = bytesio_filemap(img)
      img_fobj = fm["image"].fileobj
      hdr_fobj = (
          img_fobj if not "header" in fm else fm["header"].fileobj
      )
      img_hdr.write_to(hdr_fobj)
      img_hdr.data_to_fileobj(arr, img_fobj, rescale=False)
      raw_rt_img = img_class.from_file_map(fm)
      assert_array_equal(raw_rt_img.get_fdata(), arr)
      # Scaling makes no difference for image round trip
      fm = bytesio_filemap(img)
      img.to_file_map(fm)
      rt_img = img_class.from_file_map(fm)
      assert_array_equal(rt_img.get_fdata(), arr)
  
imports: import itertools
  import unittest
  from io import BytesIO
  import numpy
  import pytest
  from numpy.testing import assert_array_almost_equal, assert_array_equal
  from ..optpkg import optional_package
  from ..casting import sctypes_aliases, shared_range, type_info
  from ..spatialimages import HeaderDataError
  from ..spm99analyze import HeaderTypeError, Spm99AnalyzeHeader, Spm99AnalyzeImage
  from ..testing import assert_allclose_safely, bytesio_filemap, bytesio_round_trip, suppress_warnings
  from ..volumeutils import _dt_min_max, apply_read_scaling
  from .None import test_analyze
label_desc: Use image node_id 5 for calling the ImageScalingMixin obj's underlying member method code with example usage: obj.assert_null_scaling(arr, slope, inter) without return types