code: def graph_build_zero_filling(X, edge_index, node_mask: np.array):
      """subgraph building through masking the unselected nodes with zero features"""
      ret_X = X * node_mask.unsqueeze(1)
      return ret_X, edge_index
  
imports: import copy
  import torch
  import numpy
  from scipy.special import comb
  from itertools import combinations
  import torch.nn.functional
  from torch_geometric.utils import to_networkx
  from torch_geometric.data import Data, Batch, Dataset
  from torch_geometric.loader import DataLoader
label_desc: Use image node_id 5 for calling a global function with example usage: graph_build_zero_filling(X, edge_index, node_mask) and returns: ret_X,  edge_index