code: def __str__(self):
      return f'{self.contig}:{self.position}:{self.ref}:{",".join(self.alts)}'
  
imports: import gzip
  import io
  import json
  import os
  import re
  import shlex
  import subprocess
  import sys
  import time
  from typing import List
label_desc: Use image node_id 6 for calling the Variant obj's underlying member method code with example usage: obj.__str__() and returns: self, str, self, str, self, str, str