code: def add_special_char(self, dict_character):
      self.beg_str = "<SOS>"
      self.end_str = "<EOS>"
      self.unknown_str = "<UKN>"
      self.pad_str = "<PAD>"
      dict_character = dict_character
      dict_character = dict_character + [
          self.unknown_str,
          self.beg_str,
          self.end_str,
          self.pad_str,
      ]
      return dict_character
  
file_path: PaddleOCR/ppocr/postprocess/table_postprocess.py
imports: import numpy
  import paddle
  from .rec_postprocess import AttnLabelDecode
label_desc: Use image node_id 2 for calling the TableMasterLabelDecode obj's underlying member method code with example usage: obj.add_special_char(dict_character) and returns: dict_character