class_docstr: This is a feature extraction mixin used to provide saving/loading functionality for sequential and image feature
  extractors.
class_docstr_tok: ["This","is","a","feature","extraction","mixin","used","to","provide","saving\/loading","functionality","for","sequential","and","image","feature","extractors","."]
docstr: Serializes this instance to a JSON string.
  
  Returns:
      `str`: String containing all the attributes that make up this feature_extractor instance in JSON format.
docstr_tok: ["Serializes","this","instance","to","a","JSON","string",".","Returns",":","`","str","`",":","String","containing","all","the","attributes","that","make","up","this","feature_extractor","instance","in","JSON","format","."]
code: def to_json_string(self) -> str:
      """
      Serializes this instance to a JSON string.
  
      Returns:
          `str`: String containing all the attributes that make up this feature_extractor instance in JSON format.
      """
      dictionary = self.to_dict()
  
      for key, value in dictionary.items():
          if isinstance(value, np.ndarray):
              dictionary[key] = value.tolist()
  
      # make sure private name "_processor_class" is correctly
      # saved as "processor_class"
      _processor_class = dictionary.pop("_processor_class", None)
      if _processor_class is not None:
          dictionary["processor_class"] = _processor_class
  
      return json.dumps(dictionary, indent=2, sort_keys=True) + "\n"
  
imports: import copy
  import json
  import os
  from collections import UserDict
  from typing import TYPE_CHECKING, Any, Dict, Optional, Tuple, Union
  import numpy
  from .dynamic_module_utils import custom_object_save
  from .utils import FEATURE_EXTRACTOR_NAME, PushToHubMixin, TensorType, cached_file, copy_func, download_url, is_flax_available, is_jax_tensor, is_numpy_array, is_offline_mode, is_remote_url, is_tf_available, is_torch_available, is_torch_device, logging, torch_required
label_desc: Use image node_id 9 for calling the FeatureExtractionMixin obj's underlying member method code with example usage: obj.to_json_string() and returns: unknown