code: def process_sub_grow(ref, alt_str):
      
      if len(alt_str) == 0:
          raise exceptions.InvalidRecordException("Invalid VCF, empty ALT")
      elif len(alt_str) == 1:
          if ref[0] == alt_str[0]:
              return record.Substitution(record.DEL, alt_str)
          else:
              return record.Substitution(record.INDEL, alt_str)
      else:
          return record.Substitution(record.INDEL, alt_str)
docs: Process substution where the string grows