enh: minor edits to minimize conflicts with #28.

Author: oesteban

src/nifreeze/data/dmri.py

@@ -130,9 +130,9 @@ def set_transform(self, index: int, affine: np.ndarray, order: int = 3) -> None:
         if not Path(self._filepath).exists():
             self.to_filename(self._filepath)
 
-        reference = namedtuple("ImageGrid", ("shape", "affine"))(
-            shape=self.dataobj.shape[:3], affine=self.affine
-        )
+        ImageGrid = namedtuple("ImageGrid", ("shape", "affine"))
+        reference = ImageGrid(shape=self.dataobj.shape[:3], affine=self.affine)
+
         xform = Affine(matrix=affine, reference=reference)
         bvec = self.gradients[:3, index]
 

src/nifreeze/registration/ants.py

@@ -469,7 +469,8 @@ def _run_registration(
         registration.inputs.fixed_image_masks = ["NULL", bmask_img]
 
     if em_affines is not None and np.any(em_affines[vol_idx, ...]):
-        reference = namedtuple("ImageGrid", ("shape", "affine"))(shape=shape, affine=affine)
+        ImageGrid = namedtuple("ImageGrid", ("shape", "affine"))
+        reference = ImageGrid(shape=shape, affine=affine)
         initial_xform = Affine(matrix=em_affines[vol_idx], reference=reference)
         mat_file = dirname / f"init_{i_iter}_{vol_idx:05d}.mat"
         initial_xform.to_filename(mat_file, fmt="itk")