- Slicing bugfix.

- Sort imports.
- Make sitk-elastix optional again.

tests/test_slicing.py

@@ -0,0 +1,23 @@
+from itertools import combinations_with_replacement
+from numbers import Number
+
+import numpy as np
+import pytest
+from ndbioimage import Imread
+
+r = np.random.randint(0, 255, (64, 64, 2, 3, 4))
+im = Imread(r)
+a = np.array(im)
+
+
+@pytest.mark.parametrize('s', combinations_with_replacement(
+    (0, -1, 1, slice(None), slice(0, 1), slice(-1, 0), slice(1, 1)), 5))
+def test_slicing(s):
+    s_im, s_a = im[s], a[s]
+    if isinstance(s_a, Number):
+        assert isinstance(s_im, Number)
+        assert s_im == s_a
+    else:
+        assert isinstance(s_im, Imread)
+        assert s_im.shape == s_a.shape
+        assert np.all(s_im == s_a)