This function deletes a previously defined generic function method.
Syntax
(undefmethod <generic-function-name> <index>)
where <index> is the index of the method to be deleted for
the generic function. If the symbol * is used for <index>,
then all the methods for the generic function will be deleted.
(This is different from the undefgeneric command because the header
is not removed.) If * is used for <genericfunctionname>,
then * must also be specified for <index>, and all the methods
for all generic functions will be removed. This function removes
the specified method for a generic function, but even if the method
removed is the last one, the generic function header is not removed.
The undefmethod command can be used to remove methods at any time.
Exceptions: A method may not be deleted when it or any of the
other methods for the same generic function are executing. This
function has no return value.