code: def get_num_interests(fpl):
      interests = meta_feature_extractor.get_feature_value(
          fpl, "interest"
      )
      new_features = {"num_interests": len(interests)}
      return new_features
  
file_path: model-analysis/tensorflow_model_analysis/extractors/legacy_meta_feature_extractor_test.py
imports: import apache_beam
  from apache_beam.testing import util
  import numpy
  import tensorflow
  from tensorflow_model_analysis import constants
  from tensorflow_model_analysis.api import types
  from tensorflow_model_analysis.eval_saved_model import testutil
  from tensorflow_model_analysis.extractors import legacy_meta_feature_extractor
  from tensorflow_model_analysis.extractors import slice_key_extractor
  from tensorflow_model_analysis.slicer import slicer_lib
label_desc: Use image node_id 4 for calling a global function with example usage: get_num_interests(fpl) and returns: new_features