code: def test_affine_identity():
      aff = AffineTransform.identity("ijk")
      assert_array_equal(aff.affine, np.eye(4))
      assert aff.function_domain == aff.function_range
      # AffineTransform's aren't CoordinateMaps, so
      # they don't have "function" attributes
      assert not hasattr(aff, "function")
  
imports: from copy import copy
  from types import SimpleNamespace
  import numpy
  from ..coordinate_map import AffineTransform, AxisError, CoordinateMap, CoordMapMaker, CoordMapMakerError, _as_coordinate_map, _fix0, append_io_dim, axmap, compose, drop_io_dim, equivalent, input_axis_index, io_axis_indices, orth_axes, product, shifted_domain_origin, shifted_range_origin
  from ..coordinate_system import CoordinateSystem, CoordinateSystemError, CoordSysMaker
  import pytest
  from numpy.testing import assert_almost_equal, assert_array_equal
label_desc: Use image node_id 23 for calling a global function with example usage: test_affine_identity() without return types