code: def model_fn(model_dir):
      preprocessor = joblib.load(
          os.path.join(model_dir, "model.joblib")
      )
      return preprocessor
  
file_path: sagemaker-python-sdk/tests/data/sip/sklearn_source_dir/inference.py
imports: from __future__ import print_function
  import sys
  from io import StringIO
  import os
  import csv
  import json
  import numpy
  import pandas
  from sklearn.externals import joblib
  from sagemaker_containers.beta.framework import content_types, encoders, env, modules, transformer, worker
label_desc: Use image node_id 4 for calling a global function with example usage: model_fn(model_dir) and returns: preprocessor