Better human readable representation for PickableSequentialChain

chainercv/links/model/pickable_sequential_chain.py

@@ -1,4 +1,5 @@
 import copy
+import inspect
 
 import chainer
 
@@ -160,3 +161,24 @@ def copy(self, *args, **kargs):
         copied._return_tuple = copy.copy(self._return_tuple)
 
         return copied
+
+    def __str__(self):
+        reps = []
+        for name in self.layer_names:
+            layer = self[name]
+            # Explore better representation by if-block.
+            if getattr(layer, '__name__', None) == '<lambda>':
+                rep = inspect.getsource(layer).strip().rstrip(',')
+            else:
+                rep = str(layer)
+            # Add indentation to each line.
+            rep = '({name}): {rep},'.format(name=name, rep=rep)
+            for line in rep.splitlines():
+                reps.append('  {line}\n'.format(line=line))
+        reps = ''.join(reps)
+        if reps:  # No newline with no layers.
+            reps = '\n' + reps
+
+        return '{cls}({layers})'.format(
+            cls=self.__class__.__name__, layers=reps,
+        )

tests/links_tests/model_tests/test_pickable_sequential_chain.py

@@ -129,6 +129,31 @@ def test_deletion_gpu(self):
         self.check_deletion()
 
 
+class TestPickableSequentialChainStr(unittest.TestCase):
+
+    def test_str(self):
+        self.l = PickableSequentialChain()
+        with self.l.init_scope():
+            for i in range(2):
+                setattr(
+                    self.l, 'l{}'.format(i),
+                    ConstantStubLink(np.random.uniform(size=(1, 3, 24, 24))))
+                setattr(
+                    self.l, 'b{}'.format(i),
+                    ConstantStubLink(np.random.uniform(size=(1, 3, 24, 24))))
+        self.assertEqual(
+            str(self.l),
+            '''\
+PickableSequentialChain(
+  (l0): ConstantStubLink(),
+  (b0): ConstantStubLink(),
+  (l1): ConstantStubLink(),
+  (b1): ConstantStubLink(),
+)''',
+        )
+        print(str(self.l))
+
+
 @testing.parameterize(
     {'pick': None},
     {'pick': 'f2'},