es)
(for-each (lambda (c)
(format out "subgraph cluster_~a {\nlabel= \"~a\"\ncolor=blue\n"
- (string-filter (car c) char-alphabetic?)
+ (if (guile-v2)
+ (string-filter char-alphabetic? (car c))
+ (string-filter (car c) char-alphabetic?))
(car c))
(for-each (lambda (n) (format out "~a\n" n)) (cdr c))
(display "}\n" out))