Sequence Graph (SGR) files.
module Biocaml_sgr: sigtype 
exception Bad of string
val of_channel : ?chr_map:(string -> string) ->
       ?increment_bp:int -> Pervasives.in_channel -> tval of_chr_lists : (string * (int * float) list) list -> tval to_channel : ?chr_map:(string -> string) ->
       ?increment_bp:int -> t -> Pervasives.out_channel -> unitval to_file : ?chr_map:(string -> string) ->
       ?increment_bp:int -> t -> string -> unit(chr,coord).val to_list : t -> (string * int * float) list(chr,coord).val to_chr_lists : t -> (string * (int * float) list) listchr, and inner lists will be in ascending order by coord.end