fix(imperative): infinite sampler support get batchsize

GitOrigin-RevId: 52e3d6524932e74432ad5c989cab3f7fddd9192f

imperative/python/megengine/data/sampler.py

@@ -326,3 +326,10 @@ class Infinite(MapSampler):
 
     def __len__(self):
         return np.iinfo(np.int64).max
+
+    def __getattr__(self, name):
+        # if attribute could not be found in Infinite,
+        # try to find it in self.sampler
+        if name not in self.__dict__:
+            return getattr(self.sampler, name)
+        return self.__dict__[name]

imperative/python/test/unit/data/test_sampler.py

@@ -7,7 +7,12 @@ import numpy as np
 import pytest
 
 from megengine.data.dataset import ArrayDataset
-from megengine.data.sampler import RandomSampler, ReplacementSampler, SequentialSampler
+from megengine.data.sampler import (
+    Infinite,
+    RandomSampler,
+    ReplacementSampler,
+    SequentialSampler,
+)
 
 
 def test_sequential_sampler():
@@ -25,6 +30,13 @@ def test_RandomSampler():
     assert indices == sorted(list(each[0] for each in sample_indices))
 
 
+def test_InfiniteSampler():
+    indices = list(range(20))
+    seque_sampler = SequentialSampler(ArrayDataset(indices), batch_size=2)
+    inf_sampler = Infinite(seque_sampler)
+    assert inf_sampler.batch_size == seque_sampler.batch_size
+
+
 def test_random_sampler_seed():
     seed = [0, 1]
     indices = list(range(20))