anchor.diff:          when (and (style-association-predicate association)
                     (funcall (style-association-predicate association) url))
           return (style-association-style association)))
  -
  -
  
positive.code: 
  (in-package :nyxt/dark-mode)
  
  (defstruct style-association
    (url)
    (predicate)
  
negative.code:                          :url "https://example.org"
                           :style (cl-css:css
                                   '((body
                                      :background-color "black")))))
                         :documentation "The style-assocations list
  provides a list of predicates/URL checkers and associated styles. When
  a style-association matches, its style will be applied. A
  style-association can be specified in multiple ways, please view the
  style-association struct for more details.")
     (constructor
      (lambda (mode)
        (initialize mode)))))
  