code: def is_gvcf_file(in_file):
      
      to_check = 100
      n = 0
      with utils.open_gzipsafe(in_file) as in_handle:
          for line in in_handle:
              if not line.startswith("##"):
                  if n > to_check:
                      break
                  n += 1
                  parts = line.split("\t")
                  # GATK
                  if parts[4] == "<NON_REF>":
                      return True
                  # strelka2
                  if parts[4] == "." and parts[7].startswith("BLOCKAVG"):
                      return True
                  # freebayes
                  if parts[4] == "<*>":
                      return True
                  # platypue
                  if parts[4] == "N" and parts[6] == "REFCALL":
                      return True
docs: Check if an input file is raw gVCF