RF: remove duplicate methods for attribute access

We discussed this at
https://github.com/nipy/nibabel/pull/391/files#r57834220

Author: matthew-brett

nibabel/streamlines/tests/test_trk.py

@@ -170,10 +170,7 @@ def test_load_complex_file_in_big_endian(self):
     def test_tractogram_file_properties(self):
         trk = TrkFile.load(DATA['simple_trk_fname'])
         assert_equal(trk.streamlines, trk.tractogram.streamlines)
-        assert_equal(trk.get_streamlines(), trk.streamlines)
-        assert_equal(trk.get_tractogram(), trk.tractogram)
-        assert_equal(trk.get_header(), trk.header)
-        assert_array_equal(trk.get_affine(), trk.header[Field.VOXEL_TO_RASMM])
+        assert_array_equal(trk.affine, trk.header[Field.VOXEL_TO_RASMM])
 
     def test_write_empty_file(self):
         tractogram = Tractogram(affine_to_rasmm=np.eye(4))

nibabel/streamlines/tractogram_file.py

@@ -51,21 +51,9 @@ def header(self):
 
     @property
     def affine(self):
+        """ voxmm -> rasmm affine. """
         return self.header.get(Field.VOXEL_TO_RASMM)
 
-    def get_tractogram(self):
-        return self.tractogram
-
-    def get_streamlines(self):
-        return self.streamlines
-
-    def get_header(self):
-        return self.header
-
-    def get_affine(self):
-        """ Returns vox -> rasmm affine. """
-        return self.affine
-
     @abstractclassmethod
     def is_correct_format(cls, fileobj):
         """ Checks if the file has the right streamlines file format.