+ (:documentation "Returns the weight of an edge. This defaults
+to 1.0 and can only be altered if the edge is a sub-class of
+`weighted-edge-mixin`."))
+
+(defgeneric (setf dot-attribute-value) (value attribute thing)
+ )
+
+(defgeneric dot-attribute-value (attribute thing)
+ )
+
+(defgeneric graph->dot-external (graph file-name &key type)
+ )
+
+(defgeneric ensure-valid-dot-attribute (key object)
+ )
+
+(defgeneric write-name-for-dot (attribute stream)
+ )
+
+