raw_to_item_error = [
| `header_line_not_first of int
| `header_line_without_version of (string * string) list
| `header_line_wrong_sorting of string
| `invalid_header_tag of int * string
| `invalid_tag_value_list of int * string list
| `reference_sequence_not_found of raw_alignment
| parse_optional_error
| parse_cigar_error
| `wrong_flag of raw_alignment
| `wrong_mapq of raw_alignment
| `wrong_pnext of raw_alignment
| `wrong_pos of raw_alignment
| `wrong_qname of raw_alignment
| `wrong_tlen of raw_alignment ]