(
  (a (b c)),
  (b (a c)),
  (c (a b d)),
  (d (c))
)

(
  (a (b 1.0 c 2.0)),
  (b (a 1.0 c 1.0)),
  (c (a 1.3 b 7.2 d 10.5)),
  (d (c -10.5))
)

(
  (a (b 1.0 c 2.0)),
  (b (a 1.0 c 1.0)),
  (c (a 1.3 b 7.2 d 10.5)),
  (d (c -10.5))
)

(define (get-vertices graph) ;; gets all the vertices from a graph
  ...)

(define (get-edges graph) ;; gets all the edges from a graph
  ...)

(define (get-weight vertex-from vertex-to) ;; get the weight of a specific vertex
  ...)

{
 :a {:b 3 :c 4}
 :b {:a 1}
 :c {}
}

(defclass tree ()
  ((node :accessor node :initarg :node)
   (children :accessor children :initarg :children)))

data Tree a = Null | Node Tree a Tree