code: def wkt_string():
      string = (
          "POLYGON((-78.046875 46.377254205100286,-75.76171874999999 43.32517767999295,-71.279296875 "
          "46.55886030311717,-78.046875 46.377254205100286))"
      )
      return string
  
imports: import re
  import threading
  from datetime import datetime
  from functools import reduce
  from os import environ
  from os.path import abspath, dirname, exists, isfile, join
  import pytest
  import yaml
  from pytest_socket import disable_socket
  from vcr import VCR
  import sentinelsat
  from sentinelsat import SentinelAPI, geojson_to_wkt, read_geojson
  from .custom_serializer import BinaryContentSerializer
label_desc: Use image node_id 15 for calling a global function with example usage: wkt_string() and returns: string