code: def to_json(self):
      return json.dumps(self.to_dict(), cls=NumPyEncoder)
  
imports: import json
  import logging
  import numpy
  import pandas
  from collections import namedtuple
  from joblib import Parallel, delayed, cpu_count
  from scipy.stats import entropy
  from scipy.spatial.distance import pdist, squareform
  from sklearn.manifold import MDS, TSNE
  from pyLDAvis.utils import NumPyEncoder
label_desc: Use image node_id 3 for calling the PreparedData obj's underlying member method code with example usage: obj.to_json() and returns: json