Assert that all images in subject list have different names

Resolves #35

tests/test_images_dataset.py

@@ -76,6 +76,13 @@ def test_wrong_subjects_list(self):
             self.iterate_dataset([[Image('t1', 'nopath', INTENSITY)]])
         with self.assertRaises(TypeError):
             self.iterate_dataset([[Image('t1', 5, INTENSITY)]])
+        with self.assertRaises(KeyError):
+            with tempfile.NamedTemporaryFile() as f:
+                images = [
+                    Image('t1', f.name, INTENSITY),
+                    Image('t1', f.name, INTENSITY),
+                ]
+            self.iterate_dataset([images])
         with self.assertRaises(ValueError):
             path = self.dir / 'test.txt'
             path.touch()

torchio/dataset/images.py

@@ -54,25 +54,41 @@ def __getitem__(self, index):
 
     @staticmethod
     def parse_subjects_list(subjects_list):
+        # Check that it's list or tuple
         if not isinstance(subjects_list, Sequence):
             raise TypeError(
                 f'Subject list must be a sequence, not {type(subjects_list)}')
+
+        # Check that it's not empty
         if not subjects_list:
             raise ValueError('Subjects list is empty')
+
+        # Check each element
         for subject_images in subjects_list:
+            # Check that each element is a list
             if not isinstance(subject_images, Sequence):
                 message = (
                     'Subject images list must be a sequence'
                     f', not {type(subject_images)}'
                 )
                 raise TypeError(message)
+
+            # Check that there are only instances of Image
+            # and all images have different names
+            names = []
             for image in subject_images:
                 if not isinstance(image, Image):
                     message = (
                         'Subject list elements must be instances of'
                         f' torchio.Image, not {type(image)}'
                     )
                     raise TypeError(message)
+                if image.name in names:
+                    message = (
+                        f'Two images with name "{image.name}" found in list'
+                    )
+                    raise KeyError(message)
+                names.append(image.name)
 
     @staticmethod
     def save_sample(sample, output_paths_dict):