code: def reduce_func(nodes):
      """
  
      Description
      -----------
      Collect messages and update node representations.
  
      Parameters
      ----------
      nodes : NodeBatch
          A batch of nodes.
  
      Returns
      -------
      dict mapping 'hv_new' to Float32 tensor of shape (V, K * T)
          Updated node representations. V for the number of nodes, K for the number of
          radial filters and T for the number of features to use
          (types of atomic number in the paper).
      """
      return {"hv_new": nodes.mailbox["m"].sum(1)}
  
file_path: dgl/python/dgl/nn/pytorch/conv/atomicconv.py
imports: import numpy
  import torch
  import torch.nn
label_desc: Use image node_id 2 for calling a global function with example usage: reduce_func(nodes) and returns: dict