code: def test_matrix_identity():
      # Arrange
      im = hopper("RGB")
      # fmt: off
      identity_matrix = (
          1, 0, 0, 0,
          0, 1, 0, 0,
          0, 0, 1, 0)
      # fmt: on
      assert im.mode == "RGB"
  
      # Act
      # Convert with an identity matrix
      converted_im = im.convert(mode="RGB", matrix=identity_matrix)
  
      # Assert
      # No change
      assert_image_equal(converted_im, im)
  
imports: from __future__ import annotations
  import pytest
  from PIL import Image
  from .helper import assert_image, assert_image_equal, assert_image_similar, hopper
label_desc: Use image node_id 23 for calling a global function with example usage: test_matrix_identity() without return types