code: def xmoe_2d():
      """Two-dimensional hierarchical mixture of 16 experts."""
      hparams = xmoe_top_2()
      hparams.decoder_layers = ["att", "hmoe"] * 4
      hparams.mesh_shape = "b0:2;b1:4"
      hparams.outer_batch_size = 4
      hparams.layout = (
          "outer_batch:b0;inner_batch:b1,expert_x:b1,expert_y:b0"
      )
      hparams.moe_num_experts = [4, 4]
      return hparams
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from tensor2tensor.models import mtf_transformer
  from tensor2tensor.models import mtf_transformer2
  from tensor2tensor.models.research import moe
  from tensor2tensor.utils import registry
label_desc: Use image node_id 10 for calling a global function with example usage: xmoe_2d() and returns: hparams