[MAINT] Move merge_nifti_images_in_time_dimension_task in dwi tasks module

[NicolasGensollen]

This PR proposes to move the adapter function merge_nifti_images_in_time_dimension_task from clinica.utils.image to clinica.pipelines.dwi.preprocessing.t1.tasks where other tasks for this pipeline are defined.
The function definition is kept in the image module.

[AliceJoubert]

Thanks Nicolas ! I juste have a question ; should those functions be unit tested ? ì don't think I saw any corresponding unit test

[NicolasGensollen]

Thanks Nicolas ! I juste have a question ; should those functions be unit tested ? ì don't think I saw any corresponding unit test

Thanks for the review @AliceJoubert !

The function merge_nifti_images_in_time_dimension is unit tested here:

clinica/test/unittests/utils/test_image.py

Lines 46 to 83 in 3fdfea6

	def test_merge_nifti_images_in_time_dimension_wrong_file_number(tmp_path):
	from clinica.utils.image import merge_nifti_images_in_time_dimension
	with pytest.raises(
	ValueError,
	match="At least 2 files are required.",
	):
	merge_nifti_images_in_time_dimension(())
	merge_nifti_images_in_time_dimension((tmp_path / "vol1.nii.gz"))
	def test_merge_nifti_images_in_time_dimension_non_existing_file(tmp_path):
	from clinica.utils.image import merge_nifti_images_in_time_dimension
	with pytest.raises(
	FileNotFoundError,
	match="the following",
	):
	merge_nifti_images_in_time_dimension(
	(tmp_path / "vol1.nii.gz", tmp_path / "vol2.nii.gz")
	)
	def test_merge_nifti_images_in_time_dimension_wrong_dimension(tmp_path):
	from clinica.utils.image import merge_nifti_images_in_time_dimension
	for i, input_data in enumerate((np.zeros((5, 5, 5, 10)), np.zeros((5, 5)))):
	img = nib.Nifti1Image(input_data, affine=np.eye(4))
	nib.save(img, tmp_path / f"foo{i}.nii.gz")
	with pytest.raises(
	ValueError,
	match="Only 3D or 4D images can be concatenated.",
	):
	merge_nifti_images_in_time_dimension(
	tuple(tmp_path / f"foo{i}.nii.gz" for i in range(2))
	)

The adapter merge_nifti_images_in_time_dimension_task isn't tested by the unit test suite since it is a simple wrapper. It is indirectly tested by the non regression tests though.