[nix] extend tests and comments

Author: sprenger

neo/rawio/nixrawio.py

@@ -238,7 +238,9 @@ def _parse_header(self):
                     if da.type != "neo.analogsignal":
                         continue
                     anasig_id = da.name.split('.')[-2]
-                    # skip already annotated signals
+                    # skip already annotated signals as each channel already
+                    # contains the complete set of annotations and
+                    # array_annotations
                     if anasig_id in annotated_anasigs:
                         continue
                     annotated_anasigs.append(anasig_id)

neo/test/iotest/test_nixio_fr.py

@@ -134,6 +134,9 @@ def test_annotations(self):
             assert 'venue' in frbl.segments[0].events[0].annotations
             assert 'evven' in frbl.segments[0].events[1].annotations
             assert 'custom_id' in frbl.segments[0].analogsignals[0].array_annotations
+            for anasig in frbl.segments[0].analogsignals:
+                for value in anasig.array_annotations.values():
+                    assert anasig.shape[-1] == len(value)
         os.remove(self.testfilename)