code: def from_string(s):
      fields = s.split(":")
      contig = fields[0]
      pos = fields[1]
      ref = fields[2]
      alts = fields[3].split(",")
      return Variant(contig, pos, ref, 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 2 for calling the Variant obj's underlying member method code with example usage: obj.from_string(s) and returns: Variant