allow inherits in json file

all_base_includes.ly

@@ -2,6 +2,7 @@
 
 #(if (defined? 'LAYOUT) #f (load (string-append (dirname (current-filename)) file-name-separator-string "json_parser.scm")))
 #(use-modules (json parser))
+\include "resolve_inherits.ly"
 \include "basic_format_and_style_settings.ly"
 \include "eps_file_from_song_dir.ly"
 \include "title_with_category_images.ly"

resolve_inherits.ly

@@ -0,0 +1,22 @@
+#(define (resolve-inherit-entry-in-list alist entry)
+  (let* ((key (car entry))
+        (attributes (cdr entry))
+        (inherits (assoc-ref attributes "inherits")))
+    (if inherits
+      (let* ((alist-without-entry (alist-delete key alist))
+            (inherit-entry (assoc inherits alist-without-entry))
+            (inherits-attributes (if inherit-entry (alist-copy (cdr (resolve-inherit-entry-in-list alist-without-entry inherit-entry)))))
+            (override-attributes (alist-delete "inherits" attributes)))
+        (if inherit-entry
+          (begin
+            (for-each (lambda (attribute) (assoc-set! inherits-attributes (car attribute) (cdr attribute))) override-attributes)
+            (cons key inherits-attributes)
+          )
+          (ly:error "~a can not inherit from ~a" key inherits))
+      )
+      entry
+    )))
+
+#(define (resolve-inherits alist)
+  (map (lambda (entry) (resolve-inherit-entry-in-list alist entry)) alist)
+)