anchor.diff:  - the input.")
   
      (filter-postprocessor nil
  -                         :type (or null function function-symbol)
  +                         :type (or null (function (list source string) list) function-symbol)
                            :documentation
                            "Function called when input is modified, after
   filtering the suggestions with `filter'.
  
positive.code: suggestion count is meant to be displayed or not.")
  
     (suggestion-maker #'make-suggestion
                       :documentation "Function that wraps an arbitrary
  object into a source `suggestion'.
  This is useful to set the suggestion slots such as `attributes' and `match-data'
  
negative.code: - (optional) current input.")
  
     (filter #'fuzzy-match
             :type (or null
                       (function (suggestion source string) (or null suggestion))
                       function-symbol)
             :documentation
             "Takes a `suggestion', the `source' and the `input' and return a new
  suggestion, or nil if the suggestion is discarded.")
  
     (filter-preprocessor #'delete-inexact-matches
                          :type (or null (function (list source string) list) function-symbol)
                          :documentation
                          "Function called when
  input is modified, before filtering the suggestions.
  