defgeneric

defgeneric is a Lisp macro in `eieio.el'.

(defgeneric METHOD ARGS &optional DOC-STRING)

Create a generic function METHOD.
DOC-STRING is the base documentation for this class. A generic
function has no body, as its purpose is to decide which method body
is appropriate to use. Uses `defmethod' to create methods, and calls
`defgeneric' for you. With this implementation the ARGS are
currently ignored. You can use `defgeneric' to apply specialized
top level documentation to a method.