docstr: 3 reserved keys: 'train', 'val' (optional), 'test'. Represent the split of dataset.
docstr_tok: ["3","reserved","keys",":","'train","'",",","'val","'","(","optional",")",",","'test","'",".","Represent","the","split","of","dataset","."]
code: def raw_file_names(self):
      """3 reserved keys: 'train', 'val' (optional), 'test'. Represent the split of dataset."""
      return {
          "train": "train.txt",
          "test": "test.txt",
          "val": "valid.txt",
      }
  
imports: from graph4nlp.pytorch.data.dataset import Text2TreeDataset
label_desc: Use image node_id 1 for calling the MathQADatasetForTree obj's underlying member method code with example usage: obj.raw_file_names() and returns: dict