code: def _vcf_is_strelka(variant_file, variant_metadata):
      
      if "strelka" in variant_file.lower():
          return True
      elif "NORMAL" in variant_metadata["sample_info"].keys():
          return True
      else:
          vcf_reader = vcf.Reader(open(variant_file, "r"))
          try:
              vcf_type = vcf_reader.metadata["content"]
          except KeyError:
              vcf_type = ""
          if "strelka" in vcf_type.lower():
              return True
      return False
docs: Return True if variant_file given is in strelka format