code: def __init__(self, n_particles):
      self.n_particles = n_particles
      self.graph = dgl.from_networkx(
          nx.complete_graph(self.n_particles)
      )
  
imports: import copy
  import os
  import dgl
  import networkx
  import numpy
  import torch
  from torch.utils.data import DataLoader, Dataset
label_desc: Use image node_id 1 to create a new MultiBodyGraphCollator object  with example: obj = MultiBodyGraphCollator(n_particles)