class_docstr: A classic batch object wrapper with :class:`torch_geometric.data.Data` being the
  base class, all its methods can also be used here.
docstr: Returns the number of graphs in the batch.
docstr_tok: ["Returns","the","number","of","graphs","in","the","batch","."]
code: def num_graphs(self):
      """Returns the number of graphs in the batch."""
      return self.batch[-1].item() + 1
  
imports: import torch
  from torch_geometric.data import Data
label_desc: Use image node_id 3 for calling the SimpleBatch obj's underlying member method code with example usage: obj.num_graphs() and returns: unknown