class_docstr: Gather the dataset file. Specifically for the case that only one
  annotation file is needed. For example,
  
          img_001.jpg             img_002.jpg ---> train.json
          img_003.jpg /
  
  Args:
      ann_name (str): The name of the annotation file.
docstr: Returns:
      tuple(str, str): The directory of the image and the path of
      annotation file.
docstr_tok: ["Returns",":","tuple","(","str",",","str",")",":","The","directory","of","the","image","and","the","path","of","annotation","file","."]
code: def __call__(self) -> Tuple[str, str]:
      """
      Returns:
          tuple(str, str): The directory of the image and the path of
          annotation file.
      """
  
      return (self.img_dir, osp.join(self.ann_dir, self.ann_name))
  
imports: import os.path
  from typing import Tuple
  from mmocr.registry import DATA_GATHERERS
  from .base import BaseGatherer
label_desc: Use image node_id 2 for calling the MonoGatherer obj's underlying member method code with example usage: obj.__call__() and returns: self,  osp