raw_to_item = [
  | `comment_after_end_of_header of int * string
  | `duplicate_in_reference_sequence_dictionary of reference_sequence array
  | `header_after_end_of_header of int * (string * (string * string) list)
  | `header_line_not_first of int
  | `header_line_without_version of (string * string) list
  | `header_line_wrong_sorting of string
  | `missing_ref_sequence_length of (string * string) list
  | `missing_ref_sequence_name of (string * string) list
  | `wrong_cigar_text of string
  | `wrong_flag of raw_alignment
  | `wrong_mapq of raw_alignment
  | `wrong_phred_scores of raw_alignment
  | `wrong_pnext of raw_alignment
  | `wrong_pos of raw_alignment
  | `wrong_qname of raw_alignment
  | `wrong_ref_sequence_length of (string * string) list
  | `wrong_tlen of raw_alignment
  | optional_content_parsing
  ]