added button in Auto Exam Group (doesnt work)

exam_helper/exam_helper/doctype/auto_exam_group/auto_exam_group.json

@@ -9,7 +9,8 @@
  "engine": "InnoDB",
  "field_order": [
   "date",
-  "session"
+  "session",
+  "generate_exam_group"
  ],
  "fields": [
   {
@@ -26,12 +27,17 @@
    "label": "Session",
    "options": "Forenoon\nAfternoon",
    "reqd": 1
+  },
+  {
+   "fieldname": "generate_exam_group",
+   "fieldtype": "Button",
+   "label": "Generate exam group"
   }
  ],
  "index_web_pages_for_search": 1,
  "is_virtual": 1,
  "links": [],
- "modified": "2023-04-04 17:55:32.735126",
+ "modified": "2023-04-04 19:10:48.073906",
  "modified_by": "Administrator",
  "module": "Exam Helper",
  "name": "Auto Exam Group",