module Slot:sig..end
typet =Printexc.backtrace_slot
val is_raise : t -> boolis_raise slot is true when slot refers to a raising
      point in the code, and false when it comes from a simple
      function call.
val is_inline : t -> boolis_inline slot is true when slot refers to a call
      that got inlined by the compiler, and false when it comes from
      any other context.
val location : t -> Printexc.location optionlocation slot returns the location information of the slot,
      if available, and None otherwise.
Some possible reasons for failing to return a location are as follow:
-g)val name : t -> string optionname slot returns the name of the function or definition
      enclosing the location referred to by the slot.
name slot returns None if the name is unavailable, which
      may happen for the same reasons as location returning None.
val format : int -> t -> string optionformat pos slot returns the string representation of slot as
      raw_backtrace_to_string would format it, assuming it is the
      pos-th element of the backtrace: the 0-th element is
      pretty-printed differently than the others.
Whole-backtrace printing functions also skip some uninformative
      slots; in that case, format pos slot returns None.