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.
code: def __init__(self, ann_name: str, **kwargs) -> None:
      super().__init__(**kwargs)
  
      self.ann_name = 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 1 to create a new MonoGatherer object from inherited base classes: BaseGatherer with example: obj = MonoGatherer(ann_name)