class_docstr: Simple Stage that stack GNN layers
code: def __init__(self, dim_in, dim_out, num_layers):
      super(GNNStackStage, self).__init__()
      for i in range(num_layers):
          d_in = dim_in if i == 0 else dim_out
          layer = GCNConv(d_in, dim_out)
          self.add_module("layer{}".format(i), layer)
      self.dim_out = dim_out
  
file_path: GraphGym/graphgym/contrib/stage/example.py
imports: import torch.nn
  import torch.nn.functional
  from torch_geometric.nn import GCNConv
  from graphgym.config import cfg
  from graphgym.register import register_stage
label_desc: Use image node_id 1 to create a new GNNStackStage object from inherited base classes: nn with example: obj = GNNStackStage(dim_in, dim_out, num_layers)