code: def _test_simple_reduce_axis(self, shard_x):
      X = Tensor.ones(256, 256).contiguous().realize()
      X.shard_((d0, d1), shard_x)
      O = X.sum(axis=1)
      np.testing.assert_allclose(O.numpy(), 256)
  
imports: import functools
  import unittest
  from tinygrad import Tensor, Device, nn, GlobalCounters
  from tinygrad.device import _BufferCopy
  from tinygrad.helpers import CI
  from tinygrad.jit import TinyJit
  from tinygrad.nn.state import get_parameters
  import numpy
label_desc: Use image node_id 13 for calling the TestMultiTensor obj's underlying member method code with example usage: obj._test_simple_reduce_axis(shard_x) without return types