class_docstr: A mini client example that reads some data file and formats
  it for the post call to predict
code: def post(self, data_file):
      output_json = self.process_data(data_file)
      res = requests.post(self.url, data=output_json)
      print(f"{res}: {res.text}")
      return res
  
imports: import json
  import requests
  from igel.preprocessing import handle_missing_values, read_data_to_df
label_desc: Use image node_id 3 for calling the IgelClient obj's underlying member method code with example usage: obj.post(data_file) and returns: res