module Column: sig .. end
type 'a t 
val create : ?align:Ascii_table.Align.t ->
       ?min_width:int ->
       ?max_width:int ->
       ?show:[ `If_not_empty | `No | `Yes ] ->
       string -> ('a -> string) -> 'a t
creates a column given the header and the to-string function
val create_attr : ?align:Ascii_table.Align.t ->
       ?min_width:int ->
       ?max_width:int ->
       ?show:[ `If_not_empty | `No | `Yes ] ->
       string -> ('a -> Console.Ansi.attr list * string) -> 'a t
like create, except that the to_string function must provide a list of
      attributes.