anchor.diff:      (value option)
     (stringp value)
     "~A should be a string" value)
  +
  +(define-option-validator integer-configuration-schema-option-type
  +    (value option)
  +  (integerp value)
  +  "~A should be an integer" value)
   
   (define-option-validator one-of-configuration-schema-option-type
       (value option)
  
positive.code: 
  (defclass text-configuration-schema-option-type (configuration-schema-option-type)
    ()
    (:documentation "Fill in some text"))
  
  (defmethod title ((type text-configuration-schema-option-type))
    "Text")
  
  (defclass list-configuration-schema-option-type (configuration-schema-option-type)
    ((options :initarg :options
  
negative.code:   (declare (ignore args))
    (make-instance 'boolean-configuration-schema-option-type))
  
  (define-configuration-schema-option-type :integer (&rest args)
    (declare (ignore args))
    (make-instance 'integer-configuration-schema-option-type))
  
  (define-configuration-schema-option-type :sexp (&rest args)
    (declare (ignore args))
    (make-instance 'sexp-configuration-schema-option-type))
  