class_docstr: Prepare data for open vocabulary detection models specified by "prefix".
class_docstr_tok: ["Prepare","data","for","open","vocabulary","detection","models","specified","by","``","prefix","''","."]
code: def image_meta_key(self):
      return f"{self.prefix}_{IMAGE_META}"
  
imports: import logging
  import warnings
  from typing import Callable, Dict, List, Optional, Union
  import numpy
  import PIL
  from PIL import ImageFile
  from torch import nn
  from ..constants import COLUMN, IMAGE, IMAGE_META, IMAGE_VALID_NUM, PROMPT, TEXT
  from .collator import ListCollator, PadCollator
  from .utils import is_rois_input
label_desc: Use image node_id 3 for calling the OVDProcessor obj's underlying member method code with example usage: obj.image_meta_key() and returns: self, str, IMAGE_META