class_docstr: Prepare categorical data for the model specified by "prefix".
  For multiple models requiring categorical data, we need to create a CategoricalProcessor
  for each related model so that they will have independent input.
code: def categorical_key(self):
      return f"{self.prefix}_{CATEGORICAL}"
  
file_path: autogluon/multimodal/src/autogluon/multimodal/data/process_categorical.py
imports: from typing import Any, Dict, List, Optional, Union
  import numpy
  from torch import nn
  from ..constants import CATEGORICAL, COLUMN
  from .collator import StackCollator, TupleCollator
label_desc: Use image node_id 2 for calling the CategoricalProcessor obj's underlying member method code with example usage: obj.categorical_key() and returns: self, str, CATEGORICAL